CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
What it is
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) contain a heap inspection vulnerability that could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.
What to do
Schedule the vendor fix into this week’s change window, prioritising internet-facing and business-critical systems. Confirm the fix is applied everywhere, not just where it was easy.
- Priority
- This week: Schedule into this week’s change window.
- Severity (CVSS)
- 8.6 high
- CISA assessment (SSVC)
- actively exploited; attackers can automate it at scale; partial control or data exposure
- Exploit probability (EPSS, 30 days)
- 1.0%, higher than 62% of all CVEs
- Added to CISA KEV
- 11 August 2026
- CISA fix-by date
- 14 August 2026 (US federal agencies; a sensible deadline for everyone)
- Ransomware use
- Not known
- Weakness
- CWE-244
References
- NIST NVD entry
- CISA KEV entry
- sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-a
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349
Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.