# CVE-2026-20073: Cisco Secure Firewall ASA and FTD access control bypass

Source: https://junglewise.ai/threats/cve-2026-20073-cisco-secure-firewall-asa-and-ftd-access-control-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-04. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-20073 · Severity: medium · CVSS 5.8 · Published 2026-03-04

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Threat Defense (FTD) are devices that protect networks by controlling which traffic is allowed through. A memory exhaustion bug in clustered deployments can cause access control rules to load incompletely, allowing attackers to send traffic that should be blocked directly into protected networks, bypassing security controls designed to keep intruders out.

Technologies: [Cisco Secure Firewall Adaptive Security Appliance Software](https://junglewise.ai/threats/technologies/secure-firewall-adaptive-security-appliance-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-2026-20073 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20073 being exploited in the wild.

**How severe is CVE-2026-20073?** Medium severity, with a CVSS score of 5.8, published 4 March 2026.

**Which products and versions are affected?** Cisco Secure Firewall Adaptive Security Appliance Software Multiple versions affected (see vendor advisory for specific ranges); Cisco Secure Firewall Threat Defense Software Multiple versions affected (see vendor advisory for specific ranges).

**Is there a fix for CVE-2026-20073?** A patch was published on 2026-03-04: Cisco released software updates to address this vulnerability Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-20073 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20073?** Check whether you run Cisco Secure Firewall Adaptive Security Appliance Software or Cisco Secure Firewall Threat Defense 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

This vulnerability is a improper error handling issue (CWE-284) affecting clustered Cisco Secure Firewall ASA and FTD deployments. When a node joins a cluster and encounters memory exhaustion during access control list (ACL) replication, incomplete ACL rules are installed, resulting in either dropped legitimate traffic or permit of traffic that should be denied. An unauthenticated remote attacker can exploit this by sending traffic through the affected device to bypass access controls and reach protected internal networks. The attack requires the device to be deployed in a cluster configuration and to experience memory pressure during rule synchronization. Cisco has released software patches to address this vulnerability; no workarounds are available.

## Affected products

- Cisco Secure Firewall Adaptive Security Appliance Software Multiple versions affected (see vendor advisory for specific ranges)
- Cisco Secure Firewall Threat Defense Software Multiple versions affected (see vendor advisory for specific ranges)

## Timeline

- 2026-03-04: disclosed: Vulnerability disclosed by Cisco
- 2026-03-04: patched: Cisco released software updates to address this vulnerability

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-aclbypass-dos-CVxVRSvQ](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-aclbypass-dos-CVxVRSvQ)

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- [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)