Exploited vulnerability · CISA KEV

Is CVE-2026-20349 exploited? Yes: in CISA KEV since 11 Aug 2026

Gociux · Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2026-20349, Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 11 Aug 2026, the day it was published. It affects Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD), an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

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

1. Check whether you run it. Look for Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) in your asset inventory, including appliances and cloud images. Stack check lists every exploited Cisco CVE at once.
2. Apply the fix. Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 11 Aug 2026.
4. Get told next time. Email alerts when CISA adds a CVE for Cisco.

References

• sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaf
• nvd.nist.gov/vuln/detail/CVE-2026-20349

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in August 2026 · Cisco scorecard · act-now radar.