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Full vulnerability report · 2026
CVE-2026-59250High confidence

Megaco flex scanner buffer overflow via oversized property parm name

Erlang · OTP

Official source article: GitHub GHSA-7XGH-GMGF-Q2G7 ↗. Check the applicable product and release in the original source.

8.3HighCVSS 4.0
Recommended action
Patch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.78% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Erlang OTP and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourceerlangVendor fix publishedDebian records a fixed source-package version for this release.1:27.3.4.1+dfsg-1+deb13u3Debian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourceerlangAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourceerlangVendor fix publishedDebian records a fixed source-package version for this release.1:29.0.4+dfsg-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourceerlangVendor fix publishedDebian records a fixed source-package version for this release.1:29.0.4+dfsg-1Debian Security Tracker ↗Source updated 6 Oct 2026
Ubuntu 24.04 LTSnoble · standard archiveerlangVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.1:25.3.2.8+dfsg-1ubuntu4.7Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-59250 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitymegaco: Erlang/OTP Megaco Flex Scanner: Remote code execution or denial of service via oversized message
3 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • erlang27-main@aarch64 as a component of Red Hat Hardened Images
  • erlang27-main@src as a component of Red Hat Hardened Images
  • erlang27-main@x86_64 as a component of Red Hat Hardened Images
Summary
A flaw was found in the Erlang/OTP megaco flex scanner C driver. A remote, unauthenticated attacker can exploit a buffer overflow vulnerability by sending a specially crafted H.248/Megaco message with an oversized property parameter name. This can lead to memory corruption, potentially allowing for remote code execution or causing a denial of service (DoS) crash of the system. Exploitation requires network access to the megaco transport port on systems configured to use the flex scanner.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-49324

No EUVD known-exploited evidence

Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name. When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service. The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}. This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.3 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name. When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service. The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}. This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

What

Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name. When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service. The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}. This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

Why

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name. When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service. The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}. This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

Why

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-120 ↗

CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'). The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionDenial of serviceCWE-120
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-49324Official EUVD mapping

Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name. When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service. The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}. This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

Official EUVD record ↗
BSI · German · WID-SEC-2026-2533Erlang/OTP: Mehrere Schwachstellen

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Erlang/OTP ausnutzen, um einen Denial of Service Angriff durchzuführen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen sowie Daten zu manipulieren oder offenzulegen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260729Security Bulletin 29 Jul 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 29 Jul 2026, published on 29 July 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
otp: 4.9 < 4.9.1, 17.0 < 27.3.4.15, 29.0 < 29.0.4, 84adefa331c4159d432d22840663c38f155cd4c1 < 8704c8f550a11ed5f825e3c011ecb03565b79c4f, 28.0 < 28.5.0.4, 3.17.1 < 4.7.2.2, 4.8 < 4.8.3.1
Fixed
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 27 Jul 2026 · Last source change 8 Sept 2026, 01:07 UTC · CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-49324
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enrichment underway

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 17.0; 17.0 < 27.3.4.15; 28.0 < 28.5.0.4; 29.0 < 29.0.4; < 3.17.1; 3.17.1 < 4.7.2.2; 4.8 < 4.8.3.1; 4.9 < 4.9.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    OTP: < 17.0, 17.0 < 27.3.4.15, 28.0 < 28.5.0.4, 29.0 < 29.0.4, < 3.17.1, 3.17.1 < 4.7.2.2, 4.8 < 4.8.3.1, 4.9 < 4.9.1, 84adefa331c4159d432d22840663c38f155cd4c1 < 8704c8f550a11ed5f825e3c011ecb03565b79c4f · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    3.17.1 < *; R13B03 < *; 84adefa331c4159d432d22840663c38f155cd4c1 < 8704c8f550a11ed5f825e3c011ecb03565b79c4f · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    < 17.0; 17.0 < 27.3.4.15; 28.0 < 28.5.0.4; 29.0 < 29.0.4; < 3.17.1; 3.17.1 < 4.7.2.2; 4.8 < 4.8.3.1; 4.9 < 4.9.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    OTP: < 17.0, 17.0 < 27.3.4.15, 28.0 < 28.5.0.4, 29.0 < 29.0.4, < 3.17.1, 3.17.1 < 4.7.2.2, 4.8 < 4.8.3.1, 4.9 < 4.9.1, 84adefa331c4159d432d22840663c38f155cd4c1 < 8704c8f550a11ed5f825e3c011ecb03565b79c4f · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    OTP: < 17.0, 17.0 < 27.3.4.15, 28.0 < 28.5.0.4, 29.0 < 29.0.4, < 3.17.1, 3.17.1 < 4.7.2.2, 4.8 < 4.8.3.1, 4.9 < 4.9.1, 84adefa331c4159d432d22840663c38f155cd4c1 < 8704c8f550a11ed5f825e3c011ecb03565b79c4f · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
    Red Hat Product Security ↗
  4. Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-59250 to remediation: access.redhat.com/CVE-2026-59250.
    Before
    remediation: access.redhat.com/CVE-2026-59250
    After
    remediation: access.redhat.com/CVE-2026-59250
    Red Hat Product Security ↗
  5. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    Red Hat Product Security ↗
  6. Affected versionsThe structured affected or fixed version information changed.
    Before
    erlang27.src as a component of Red Hat Hardened Images
    After
    Fixed: erlang27-main@aarch64 as a component of Red Hat Hardened Images; erlang27-main@src as a component of Red Hat Hardened Images; erlang27-main@x86_64 as a component of Red Hat Hardened Images
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-59250 · cve.blacktree.nl