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Full vulnerability report · 2026
CVE-2026-91963High confidence

FreeRDP 2.0.0 through 3.30.0 Uninitialized Heap Memory Disclosure via urbdrc

FreeRDP · FreeRDP

Official source article: GitHub GHSA-HW7P-5H2R-83GQ ↗. Check the applicable product and release in the original source.

7.1HighCVSS 4.0
Recommended action
Patch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 33 structured product or package states 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:Critical, raised one band.upgradedsince 15 Sep 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • EPSS is 0.66% 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.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs FreeRDP FreeRDP 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 3 daysRemediation target: Within 90 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 33 structured product or package states 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.

6 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 2 affected package states 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 · sourcefreerdp3Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcefreerdp2Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcefreerdp3Vendor fix publishedDebian records a fixed source-package version for this release.3.31.0+dfsg-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcefreerdp3Vendor fix publishedDebian records a fixed source-package version for this release.3.31.0+dfsg-1Debian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appsfreerdp2Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 4 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivefreerdp3Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.3.31.0+dfsg-0ubuntu0.24.04.1Canonical Ubuntu Security ↗Source updated 4 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-2026-91963 · CSAF 2.0 · revision 3 · finalRed Hat Product SecurityFreeRDP: FreeRDP: Remote code execution via uninitialized heap memory disclosure
31 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • freerdp as a component of Red Hat Enterprise Linux 10
  • freerdp-devel as a component of Red Hat Enterprise Linux 10
  • freerdp-libs as a component of Red Hat Enterprise Linux 10
  • freerdp-server as a component of Red Hat Enterprise Linux 10
  • freerdp.src as a component of Red Hat Enterprise Linux 10
  • libwinpr as a component of Red Hat Enterprise Linux 10
  • libwinpr-devel as a component of Red Hat Enterprise Linux 10
  • freerdp as a component of Red Hat Enterprise Linux 6
  • freerdp-devel as a component of Red Hat Enterprise Linux 6
  • freerdp-libs as a component of Red Hat Enterprise Linux 6
  • freerdp-plugins as a component of Red Hat Enterprise Linux 6
  • freerdp.src as a component of Red Hat Enterprise Linux 6
Summary
A flaw was found in FreeRDP. An uninitialized heap memory disclosure vulnerability exists in the urbdrc USB redirection channel. A malicious Remote Desktop Protocol (RDP) server can exploit this by inducing failing USB transfers, allowing it to read uninitialized heap memory from the client. This information disclosure can defeat Address Space Layout Randomization (ASLR), potentially enabling remote code execution when chained with other memory corruption vulnerabilities.
Remediation
To reduce exposure, avoid connecting to untrusted RDP servers or disable the FreeRDP USB redirection channel if it is not required. When using the `xfreerdp` client, ensure that USB redirection is not enabled. This can be done by omitting the `/usb` or `/usb-redir` command-line options, or by explicitly disabling the `urbdrc` channel through FreeRDP configuration if available. Disabling this feature will prevent the redirection of USB devices to the remote session.
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-2026-78639

No EUVD known-exploited evidence

FreeRDP versions before 3.31.0 contain an uninitialized heap memory disclosure vulnerability in the urbdrc USB redirection channel. A malicious RDP server can induce failing USB transfers to read uninitialized heap memory from the client, defeating ASLR and enabling remote code execution when chained with memory corruption vulnerabilities.

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
7.1 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 33 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

FreeRDP versions before 3.31.0 contain an uninitialized heap memory disclosure vulnerability in the urbdrc USB redirection channel. A malicious RDP server can induce failing USB transfers to read uninitialized heap memory from the client, defeating ASLR and enabling remote code execution when chained with memory corruption vulnerabilities.

What

FreeRDP versions before 3.31.0 contain an uninitialized heap memory disclosure vulnerability in the urbdrc USB redirection channel. A malicious RDP server can induce failing USB transfers to read uninitialized heap memory from the client, defeating ASLR and enabling remote code execution when chained with memory corruption vulnerabilities.

Why

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

How

An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may execute code or commands in the affected security context.

What

FreeRDP versions before 3.31.0 contain an uninitialized heap memory disclosure vulnerability in the urbdrc USB redirection channel. A malicious RDP server can induce failing USB transfers to read uninitialized heap memory from the client, defeating ASLR and enabling remote code execution when chained with memory corruption vulnerabilities.

Why

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

How

An attacker operating through a network path may attempt exploitation when the stated preconditions are met. 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.
Reference recorded

CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.

Likely attack path
a network path → Use of Uninitialized Variable → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Passive interaction required
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-457 ↗

CWE-457: Use of Uninitialized Variable. The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

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:N/PR:N/UI:P/VC:H/VI:N/VA:N/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.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIPassiveUser interaction: A user must unknowingly interact with the vulnerable system.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VANoneVulnerable-system availability: No direct loss is represented by this metric.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 executionCWE-457Public exploit reference
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-78639Official EUVD mapping

FreeRDP versions before 3.31.0 contain an uninitialized heap memory disclosure vulnerability in the urbdrc USB redirection channel. A malicious RDP server can induce failing USB transfers to read uninitialized heap memory from the client, defeating ASLR and enabling remote code execution when chained with memory corruption vulnerabilities.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3057FreeRDP: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Ein Angreifer kann mehrere Schwachstellen in FreeRDP ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-035299FreeRDPにおける初期化されていない変数の使用に関する脆弱性

FreeRDPのバージョン3.31.0より前には、urbdrc USBリダイレクションチャネルに未初期化のヒープメモリ情報漏洩の脆弱性が存在します。悪意のあるRDPサーバーは、失敗するUSB転送を誘発してクライアントの未初期化ヒープメモリを読み取ることができ、それによってASLRを無効化します。さらに、メモリ破損の脆弱性と組み合わせることでリモートコード実行を可能にします。

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
Fixed
FreeRDP: 3.31.0
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
To reduce exposure, avoid connecting to untrusted RDP servers or disable the FreeRDP USB redirection channel if it is not required. When using the `xfreerdp` client, ensure that USB redirection is not enabled. This can be done by omitting the `/usb` or `/usb-redir` command-line options, or by explicitly disabling the `urbdrc` channel through FreeRDP configuration if available. Disabling this feature will prevent the redirection of USB devices to the remote session.
Official vendor articles1 stored document

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

04

Evidence and provenance

Published 15 Sept 2026 · Last source change 15 Sept 2026, 15:58 UTC · CWE-457 · Use of Uninitialized Variable

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 2026-09-16
European sourceENISA EUVD · EUVD-2026-78639
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

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

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2026-78639 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-78639"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: github.com/GHSA-hw7p-5h2r-83gq.
    Before
    remediation: github.com/GHSA-hw7p-5h2r-83gq
    After
    remediation: github.com/GHSA-hw7p-5h2r-83gq · vendor advisory: github.com/GHSA-hw7p-5h2r-83gq
    github.com ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-78639↗Vendor CSAF · Red Hat Product Security↗CISA Vulnrichment SSVC evidence↗CVE authority or vendor reference · GitHub GHSA-HW7P-5H2R-83GQ↗Official CVE record (CNA and ADP data)↗NVD record↗
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-2026-91963 · cve.blacktree.nl