# CVE-2026-20335: Cisco Secure Firewall ASA calculation error in security-critical context

Source: https://junglewise.ai/threats/cve-2026-20335-cisco-secure-firewall-asa-calculation-error-in-security-critical  
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-2026-20335 · Severity: high · CVSS 8.1 · Published 2026-09-16

Cisco Secure Firewall Adaptive Security Appliance (ASA) is a widely-deployed network appliance that protects corporate networks by monitoring and filtering traffic. A calculation error in security-critical operations allows authenticated attackers to bypass access controls or cause service disruptions, potentially compromising network security and availability.

Technologies: [Cisco Secure Firewall ASA Software](https://junglewise.ai/threats/technologies/secure-firewall-asa-software). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20335 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20335 being exploited in the wild.

**How severe is CVE-2026-20335?** High severity, with a CVSS score of 8.1, published 16 September 2026.

**Which products and versions are affected?** Cisco Secure Firewall ASA Software Multiple affected versions; see vendor advisory for patched releases.

**Is there a fix for CVE-2026-20335?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20335 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20335?** Check whether you run Cisco Secure Firewall ASA Software at an affected version. 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-2026-20335 is a calculation vulnerability (CWE-682) affecting Cisco Secure Firewall ASA Software that generates incorrect results used in security-critical decisions or resource management. The vulnerability requires low privileges and network access, and can be exploited without user interaction. An authenticated attacker can leverage this calculation error to achieve high impact on confidentiality, integrity, and availability. Cisco released software updates to remediate the issue; no workarounds are available.

## Affected products

- Cisco Secure Firewall ASA Software Multiple affected versions; see vendor advisory for patched releases

## Timeline

- 2026-09-16: disclosed

## 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 Secure Firewall ASA/FTD/FMC access control vulnerability](https://junglewise.ai/threats/cve-2026-20332-cisco-secure-firewall-asa-ftd-fmc-access-control-vulnerability)
- [Cisco Secure Firewall ASA and FTD DTLS denial of service](https://junglewise.ai/threats/cve-2026-20250-cisco-secure-firewall-asa-and-ftd-dtls-denial-of-service)
- [Cisco Secure Firewall improper exception handling and input validation](https://junglewise.ai/threats/cve-2026-20329-cisco-secure-firewall-improper-exception-handling-and-input)
- [Cisco Secure Firewall protection mechanism failure](https://junglewise.ai/threats/cve-2026-20331-cisco-secure-firewall-protection-mechanism-failure)