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Full vulnerability report · 2026
CVE-2026-84411High confidence

MikroTik RouterOS Integer Underflow

MikroTik · RouterOS

9.3CriticalCVSS 4.0
Recommended action
Within 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, 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 0.95% 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 MikroTik RouterOS 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.

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-2026-91836

No EUVD known-exploited evidence

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

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
9.3 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
01

What, why and how

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

What

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

Why

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

Why

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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 → Integer Underflow (Wrap or Wraparound) → 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-191 ↗

CWE-191: Integer Underflow (Wrap or Wraparound). The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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:N/VC:H/VI:H/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.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VIHighVulnerable-system integrity: A successful attack can cause a major 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-191
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-91836Official EUVD mapping

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3661MikroTik RouterOS: Schwachstelle ermöglicht Codeausführung und DoS

Ein entfernter Angreifer kann eine Schwachstelle in MikroTik RouterOS ausnutzen, um beliebigen Programmcode auszuführen oder einen Denial-of-Service-Zustand auszulösen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-992MikroTik security advisory (AV26-992)

As of September 29, 2026, MikroTik is affected by vulnerabilities in the following product:

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20261007Security Bulletin 7 Oct 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 7 Oct 2026, published on 7 October 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CISA · English · ICSA-26-272-06MikroTik RouterOS

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

Official advisory ↗
CSIRT Italia · Italian · risolta-vulnerabilita-in-mikrotik-routerosRisolta vulnerabilità in MikroTik RouterOS

Aggiornamenti di sicurezza per MikroTik RouterOS sanano una vulnerabilità con gravità "critica". Tale vulnerabilità, qualora sfruttata, potrebbe consentire ad un utente malintenzionato remoto non autenticato di eseguire codice arbitrario con privilegi di root o di compromettere la disponibilità del servizio sui sistemi interessati.

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.
Patch available
Affected
RouterOS: 0 < 7.24
Fixed
RouterOS: 7.24
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
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 2 Oct 2026 · Last source change 3 Oct 2026, 15:52 UTC · CWE-191 · Integer Underflow (Wrap or Wraparound)

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 2026-10-03
European sourceENISA EUVD · EUVD-2026-91836
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD awaiting enrichment

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-2026-91836 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-91836"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added remediation: github.com/icsa-26-272-06.json; removed patch: cisa.gov/icsa-26-272-06; removed remediation: cisa.gov/icsa-26-272-06.
    Before
    patch: cisa.gov/icsa-26-272-06 · remediation: cisa.gov/icsa-26-272-06
    After
    remediation: github.com/icsa-26-272-06.json
    CNA ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    MikroTik RouterOS: <7.24 · Fixed: MikroTik recommends users update RouterOS to version 7.24 or later. The upgrade can be downloaded from the MikroTik website.
    After
    RouterOS: < 7.24 · Fixed: RouterOS: 7.24
    CNA ↗
  4. CVSS scoreCVSS score changed from 9.8 (CVSS 3.1 · Other authority · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) to 9.3 (CVSS 4.0 · CNA · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X).
    Before
    9.8 (CVSS 3.1 · Other authority · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
    After
    9.3 (CVSS 4.0 · CNA · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)
    CNA ↗
  5. Vendor guidanceAuthoritative vendor guidance changed: added remediation: mikrotik.com/download; removed remediation: github.com/icsa-26-272-06.json.
    Before
    remediation: github.com/icsa-26-272-06.json
    After
    remediation: mikrotik.com/download
    CNA ↗
  6. Affected versionsThe structured affected or fixed version information changed.
    Before
    MikroTik RouterOS: <7.24 · Fixed: The authority publishes remediation guidance. Confirm the exact fixed release in the linked primary advisory.
    After
    MikroTik RouterOS: <7.24 · Fixed: MikroTik recommends users update RouterOS to version 7.24 or later. The upgrade can be downloaded from the MikroTik website.
    CISA ↗
  7. Vendor guidanceAuthoritative vendor guidance changed: added mitigation: cisa.gov/icsa-26-272-06; removed patch: cisa.gov/icsa-26-272-06.
    Before
    patch: cisa.gov/icsa-26-272-06 · remediation: cisa.gov/icsa-26-272-06
    After
    mitigation: cisa.gov/icsa-26-272-06 · remediation: cisa.gov/icsa-26-272-06
    national-authority:CISA:ICSA-26-272-06 ↗
  8. Affected versionsThe structured affected or fixed version information changed.
    Before
    MikroTik RouterOS: <7.24 · Fixed: MikroTik recommends users update RouterOS to version 7.23 or later. The upgrade can be downloaded from the MikroTik website.
    After
    MikroTik RouterOS: <7.24 · Fixed: The authority publishes remediation guidance. Confirm the exact fixed release in the linked primary advisory.
    Official national cybersecurity authority ↗
  9. Affected versionsThe structured affected or fixed version information changed.
    Before
    MikroTik RouterOS: <7.24 · Fixed: The authority publishes remediation guidance. Confirm the exact fixed release in the linked primary advisory.
    After
    MikroTik RouterOS: <7.24 · Fixed: MikroTik recommends users update RouterOS to version 7.23 or later. The upgrade can be downloaded from the MikroTik website.
    CISA ↗
  10. Catalogue recordCVE added to the BlackTree catalogue.
    Official national cybersecurity authority ↗
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-2026-91836↗CVE authority or vendor reference↗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-2026-84411 · cve.blacktree.nl