Cisco Security Advisories 22nd October 2026

THREAT INTELLIGENCE

Peer Review

4.8

Proven Trust

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Critical

CVE-2026-76466, CVE-2026-76473, CVE-2026-76474

Cisco

October 22, 2026

Executive Summary

Critical flaws include Expressway root RCE CVE-2026-76466 and Unified CM issues CVE-2026-76473 and CVE-2026-76474, all CVSS 9.8.

Key Details

Affected Platform

Cisco

Attack Surface

Recommended Action

Apply vendor patch

Affected Environment

Cisco Expressway, Unified Communications products, Snort 3 based products, IOS XR ASR 9000, Secure Client, and products under PHP investigation.

Operational Impact

Root command execution on Expressway, Snort 3 engine restarts, line card resets, privilege escalation, and access control bypass.

Technical Root Cause

Persistent cookies with weak certificate validation, improper authentication, resource lifecycle flaws, out-of-bounds writes, and improper input handling.

Recommended Mitigation

Upgrade to Cisco fixed releases, including Expressway X15.5.20, Unified CM 15SU5, and Snort 3 3.12.4.0; few workarounds exist.

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Full Technical Report

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References

Cisco Security Advisories, including cisco-sa-php-october26.