# CVE-2026-20331: Cisco Secure Firewall protection mechanism failure

Source: https://junglewise.ai/threats/cve-2026-20331-cisco-secure-firewall-protection-mechanism-failure  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-20331 · Severity: critical · CVSS 9.6 · Published 2026-09-16

Cisco's Secure Firewall suite (ASA, Threat Defense, and Management Center) contains multiple critical vulnerabilities discovered during an internal security review and grouped under a single CVE. These failures in protection mechanisms could allow authenticated attackers to bypass firewall controls, escalate privileges, or compromise the appliance, directly undermining the security devices that organizations rely on to protect their networks.

Technologies: [Cisco Secure Firewall ASA Software](https://junglewise.ai/threats/technologies/secure-firewall-asa-software), [Cisco Secure Firewall Management Center Software](https://junglewise.ai/threats/technologies/secure-firewall-management-center-software), [Cisco Secure Firewall Threat Defense Software](https://junglewise.ai/threats/technologies/firepower-threat-defense-software). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20331 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20331 being exploited in the wild.

**How severe is CVE-2026-20331?** Critical severity, with a CVSS score of 9.6, published 16 September 2026.

**Which products and versions are affected?** Cisco Secure Firewall ASA Software; Cisco Secure Firewall Threat Defense Software; Cisco Secure Firewall Management Center Software.

**Is there a fix for CVE-2026-20331?** A patch was published on 2026-09: Software updates released to address vulnerabilities Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-20331 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20331?** Check whether you run Cisco Secure Firewall ASA Software, Cisco Secure Firewall Management Center Software or Cisco Secure Firewall Threat Defense Software. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

CVE-2026-20331 tracks a protection mechanism failure (CWE-693) in Cisco Secure Firewall ASA, Threat Defense (FTD), and Management Center (FMC) software. The underlying issue involves improper use of a protection mechanism that fails to defend against directed attacks. Multiple vulnerabilities are grouped under related CWE categories including improper access control (CWE-284), incorrect comparisons in security-relevant contexts (CWE-697), and other control flow and validation issues. The advisory indicates at least two related vulnerabilities are actively exploited in the wild. Attack requires authentication (PR:L per CVSS vector) and is network-reachable. Cisco has released software updates to address these issues; no workarounds are available.

## Affected products

- Cisco Secure Firewall ASA Software
- Cisco Secure Firewall Threat Defense Software
- Cisco Secure Firewall Management Center Software

## Timeline

- 2026-09-16: disclosed: Public disclosure of CVE-2026-20331 and related hardening release
- 2026: exploited: Two related vulnerabilities actively exploited in the wild at time of disclosure
- 2026-09: patched: Software updates released to address vulnerabilities

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-asaftdfmc-uvpPROhN](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-asaftdfmc-uvpPROhN)

## Related threats

- [Cisco Secure Firewall ASA and FTD SSL VPN denial of service](https://junglewise.ai/threats/cve-2026-76418-a-vulnerability-in-the-remote-access-ssl-vpn-service-of-cisco)
- [Cisco Snort 3 GRE detection engine denial of service](https://junglewise.ai/threats/cve-2026-20179-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Secure FMC SQL injection in web management interface](https://junglewise.ai/threats/cve-2026-20344-cisco-secure-fmc-sql-injection-in-web-management-interface)
- [Cisco Secure FMC arbitrary file download in download API](https://junglewise.ai/threats/cve-2026-20342-cisco-secure-fmc-arbitrary-file-download-in-download-api)
- [Cisco Secure Firewall ASA calculation error in security-critical context](https://junglewise.ai/threats/cve-2026-20335-cisco-secure-firewall-asa-calculation-error-in-security-critical)