Cisco ASA/FTD VPN flaw exploited for DoS
A remotely exploitable DoS vulnerability in Cisco ASA and Secure FTD VPN handling, CVE-2026-20349, is being actively exploited in the wild.
Sourcecert.ssi.gouv.fr — open the original
What to check
- Applies to
- The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- CISA lists CVE-2026-20349 as exploited in the wild.
CERT-FR has issued an advisory regarding CVE-2026-20349, a vulnerability affecting Cisco Adaptive Security Appliance (ASA) and Secure Firepower Threat Defense (FTD) products. The flaw allows a remote, unauthenticated attacker to trigger a denial-of-service condition, and Cisco has confirmed active exploitation of the vulnerability in the wild.
Affected versions span multiple ASA release branches (9.16.x, 9.18.x, 9.20.x, 9.22.x, 9.23.x, and 9.24.x) lacking specific security patches, as well as Secure FTD deployments without the latest security fix. Cisco published bulletin cisco-sa-asaftd-vpn-dos-dzv4mQFF on August 11, 2026, detailing the issue and providing remediation guidance. Organizations running affected ASA or FTD versions, particularly those exposing VPN services, should prioritize patching given the confirmed active exploitation.
Mentioned in this report
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1010
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