CVE-2026-20349 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD): memory-safety flaw
In plain words: The program mishandles the memory it uses to keep track of data. A specially made input can scramble that memory. Usually lets an attacker crash the program or run their own code with its permissions.
Confirmed exploited by CISA on · US federal patch deadline Aug 14, 2026
What to do
- Install Cisco's security update for Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD). If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Patch edge devices first — attackers often start scanning for them within hours of a fix.
- Never expose the device's admin page to the internet.
- After patching a device that was exposed, follow the vendor's compromise checks, end active sessions and change passwords.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: They face the internet and guard the whole network, so a flaw here can hand attackers a way in — and these devices usually run no antivirus, so break-ins go unnoticed.
The details
- Official name
- Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
- Product
- Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD)
- CISA description
- 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.
- Type of flaw
- Memory-safety flaw (CWE-244)
- Confirmed exploited
- Aug 11, 2026
- US federal patch deadline
- Aug 14, 2026
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Answering about CVE-2026-20349 ·
Questions about CVE-2026-20349
Is CVE-2026-20349 being exploited?
Yes. CISA added CVE-2026-20349 to its Known Exploited Vulnerabilities catalog on Aug 11, 2026, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2026-20349?
Install Cisco's security update for Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD). If no update exists, follow the vendor's workaround or stop using the product until one ships. Patch edge devices first — attackers often start scanning for them within hours of a fix.
Am I affected by CVE-2026-20349?
Only if you use Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD). Aimed mostly at company systems — you are affected through the companies you use, not your own phone.