CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.
CSIRTS triage
- What
- Heap inspection vulnerability in Cisco Secure Firewall ASA and FTD Remote Access SSL VPN service causes unexpected device reload.
- Who is affected
- Unauthenticated remote attackers can exploit Cisco ASA and FTD devices with Remote Access SSL VPN exposed.
- Urgency
- Critical severity; actively exploited and allows remote denial of service without authentication.
- Action
- Apply Cisco security updates for CVE-2026-20349 with urgency.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-20349
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Exploitation confirmedCVE-2026-20349Already exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 56% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-20349 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- highexploitedAL26-018 - Vulnerability affecting Cisco ASA and Secure Firewall Threat Defense Software Remote Access SSL VPN…cccs
- unknownexploitedNCSC-2026-0295 [1.00] [M/H] Vulnerability patched in Cisco Secure Firewall ASA and FTD softwarencsc-nl
- unknownexploitedCisco security advisory (AV26-807)cccs
- highexploited[NEW] [high] Cisco ASA (Adaptive Security Appliance) and Secure Firewall Threat Defense: Vulnerability enables…cert-bund
- unknownexploitedCisco Products Multiple Vulnerabilitieshkcert
- unknownexploitedVulnerability in Cisco products (August 12, 2026)cert-fr-avis
- highexploitedCVE-2026-20349: A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Securi…nvd
- highexploitedCisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SS…cisco-psirt
- highexploitedCISA Adds Three Known Exploited Vulnerabilities to Catalogcisa
Recent advisories for Cisco Secure Firewall
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- highexploitedAL26-018 - Vulnerability affecting Cisco ASA and Secure Firewall Threat Defense Software Remote Access SSL VPN…cccs · 2026-08-13
- unknownexploitedNCSC-2026-0295 [1.00] [M/H] Vulnerability patched in Cisco Secure Firewall ASA and FTD softwarencsc-nl · 2026-08-12
- highexploited[NEW] [high] Cisco ASA (Adaptive Security Appliance) and Secure Firewall Threat Defense: Vulnerability enables…cert-bund · 2026-08-12
- highexploitedCisco Secure Firewall Management Center Software Static Credential Vulnerabilitycisco-psirt · 2026-08-11
- highexploitedCVE-2026-20349: A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Securi…nvd · 2026-08-11
- highexploitedCisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SS…cisco-psirt · 2026-08-11
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