# CVE-2026-20023: Cisco Secure Firewall ASA and FTD OSPF memory corruption denial of service

Source: https://junglewise.ai/threats/cve-2026-20023-cisco-secure-firewall-asa-and-ftd-ospf-memory-corruption-denial  
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-2026-20023 · Severity: medium · CVSS 6.1 · Published 2026-03-04

Cisco Secure Firewall devices (ASA and FTD) used to protect enterprise networks have a vulnerability in their OSPF protocol implementation. An attacker on the same network segment can send specially crafted packets that cause memory corruption, forcing the firewall to reboot and interrupting network traffic and security services until the device recovers.

Technologies: [Cisco Secure Firewall Adaptive Security Appliance (ASA) Software](https://junglewise.ai/threats/technologies/secure-firewall-adaptive-security-appliance-asa-software), [Cisco Secure Firewall Threat Defense (FTD) Software](https://junglewise.ai/threats/technologies/secure-firewall-threat-defense-ftd-software). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20023 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20023 being exploited in the wild.

**How severe is CVE-2026-20023?** Medium severity, with a CVSS score of 6.1, published 4 March 2026.

**Which products and versions are affected?** Cisco Secure Firewall Adaptive Security Appliance (ASA) Software affected versions running OSPF protocol (specific versions in Cisco advisory); Cisco Secure Firewall Threat Defense (FTD) Software affected versions running OSPF protocol (specific versions in Cisco advisory).

**Is there a fix for CVE-2026-20023?** 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-2026-20023 attacked?** It is attacked from the adjacent network.

**Am I affected by CVE-2026-20023?** Check whether you run Cisco Secure Firewall Adaptive Security Appliance (ASA) Software or Cisco Secure Firewall Threat Defense (FTD) 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

Multiple memory corruption vulnerabilities exist in the OSPF protocol parser of Cisco Secure Firewall ASA and FTD software, including buffer overflows and heap corruption issues (CWE-119, CWE-787, CWE-823). The vulnerabilities stem from insufficient input validation when processing OSPF update, link-state, and other protocol packets. Attack vectors vary: some require only network adjacency and are unauthenticated (CVE-2026-20020), while others require knowledge of the OSPF secret key (CVE-2026-20024, CVE-2026-20025). Successful exploitation causes memory corruption leading to unexpected device reboot and denial of service. Cisco has released patches; no workarounds are available.

## Affected products

- Cisco Secure Firewall Adaptive Security Appliance (ASA) Software affected versions running OSPF protocol (specific versions in Cisco advisory)
- Cisco Secure Firewall Threat Defense (FTD) Software affected versions running OSPF protocol (specific versions in Cisco advisory)

## Timeline

- 2026-03-04: disclosed: Cisco Security Advisory published

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ospf-ZH8PhbSW](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ospf-ZH8PhbSW)

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