Cisco: Snort 3 security hardening release fixes out-of-bounds write, incorrect calculation, privilege management and DoS flaws across multiple products (CVE-2026-20043, CVE-2026-20236, CVE-2026-20291, CVE-2026-20356)
Severity: critical · Patch status: patched · Since 2026-10-21 · CVE-2026-20011, CVE-2026-20043, CVE-2026-20218, CVE-2026-20221, CVE-2026-20236, CVE-2026-20291, CVE-2026-20356, CVE-2026-76445, CVE-2026-76524
Cisco's Snort 3 engineering team completed an internal security review and released hardening updates addressing multiple internally discovered vulnerabilities, grouped by CWE with one CVE per class: CVE-2026-20043 (out-of-bounds write, CWE-787), CVE-2026-20236 (incorrect calculation, CWE-682), CVE-2026-20291 (improper privilege management, CWE-269) and CVE-2026-20356 (uncontrolled resource consumption, CWE-400), with a maximum CVSS of 9.0. Affected products include Cisco Cloud-delivered Firewall, Cyber Vision, Meraki MX, Secure Access, Secure Firewall Threat Defense and UTD on IOS XE; Snort 2 is not affected. The flaws were found in internal testing and are not known to be exploited. Snort 3.12.4.0, Cyber Vision 5.6.0 and various FTD releases contain fixes; CDFW, CSA and Meraki instances were updated automatically on 2026-10-21. No workarounds exist.
What to do
- Upgrade Open Source Snort 3 to 3.12.4.0 or later
- Upgrade Cisco Cyber Vision to 5.6.0 (or migrate from older releases)
- Upgrade Cisco Secure FTD to the first fixed release for your train (7.0.10, 7.2.12, 7.4.8, 7.6.6, 7.7.13, 10.0.2 or 10.1.0)
- Update UTD on Cisco IOS XE per the advisory's fixed release table
- Verify CDFW, CSA and Meraki MX devices are online so automatic Snort 3 package updates have applied
Fixed versions
- Snort 3.12.4.0
- Cyber Vision 5.6.0
- FTD 7.0.10 / 7.2.12 / 7.4.8 / 7.6.6 / 7.7.13 / 10.0.2 / 10.1.0
Sources
All live incidents on Threat Watch
