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PatchSiren cyber security CVE debrief

CVE-2026-76459 Cisco CVE debrief

Cisco has addressed multiple out-of-bounds write vulnerabilities in their NX-OS Software Security Hardening Release for October 2026. The vulnerabilities, tracked by CVE-2026-76459, are related to out-of-bounds write issues grouped under CWE-787. This security hardening release is part of Cisco's ongoing commitment to proactive security and product quality. The Cisco NX-OS engineering team conducted a comprehensive internal security review, which resulted in the identification and addressing of these vulnerabilities. Defenders should verify exposure in their Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode deployments, assess if any of the affected versions are in

Vendor
Cisco
Product
Cisco NX-OS Software
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-07
Original CVE updated
2026-10-07
Advisory published
2026-10-07
Advisory updated
2026-10-07

Who should care

Defenders responsible for Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode deployments should assess exposure and prioritize patching based on the affected versions in their environment.

Why it matters

CVE-2026-76459 out-of-bounds write vulnerabilities in Cisco NX-OS Software Security Hardening Release require verification of exposure and prioritized patching to prevent potential security impacts.

  • Verify exposure of Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode deployments.
  • Assess and prioritize patching based on affected versions.
  • Review and update inventory to ensure accurate tracking of software versions.
  • Consider compensating controls for unpatched systems.

Technical summary

CVE-2026-76459 addresses out-of-bounds write vulnerabilities in Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode. The vulnerabilities are tracked under CWE-787 and have a CVSS score of 8.8. These vulnerabilities require verification of exposure and prioritized patching to prevent potential security impacts. The Cisco NX-OS Software Security Hardening Release for October 2026 addresses these issues, and defenders should prioritize verifying exposure in their Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode deployments, assessing if any of the affected versions are in use. The CVE record and Cisco's security advisory provide details on the vulnerabilities and affected software

Defensive priority

Defenders should prioritize verifying exposure in their Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode deployments, assessing if any of the affected versions are in use.

Recommended defensive actions

  • Verify Cisco NX-OS Software and Cisco NX-OS System Software in ACI Mode versions against the list of affected versions.
  • Assess exposure based on current deployments and configurations.
  • Apply patches or updates provided by Cisco according to their security advisory.
  • Review compensating controls for exposed systems while remediation is scheduled and verified.
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review.
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented.
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and Cisco's security advisory provide details on the vulnerabilities and affected software versions. However, the corpus does not establish specific exploitation instances or impacts, requiring verification from official sources.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-76459 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-76459

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-76459 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-76459

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.