Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability
Affects Cisco Secure Firewall ASA and FTD software releases with SSL VPN (webvpn), IKEv2 remote access VPN with client services, or Zero Trust Network Access (FTD only) enabled. No fixed release is listed in the facts.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software are affected when their Remote Access SSL VPN service is enabled. An unauthenticated remote attacker could send a specially crafted HTTP request to make the device reload unexpectedly, causing a denial of service that interrupts network protection and VPN access.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
Timeline
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CVE published
- CISA remediation deadline
Due date for US federal agencies to patch
- Record last updated
Affected versions
- Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
9.16.1, 9.16.1.28, 9.16.2, 9.16.2.3, 9.16.2.7, 9.16.2.11, 9.16.2.13, 9.16.2.14, 9.16.3.3, 9.16.3, 9.16.3.14, 9.18.1, 9.16.3.15, 9.18.1.3, 9.18.2, 9.16.3.19, 9.16.3.23, 9.18.2.5, 9.16.4, 9.18.2.7, 9.19.1, 9.16.4.9, 9.18.2.8, 9.16.4.14, 9.18.3, 9.19.1.5, 9.16.4.18, 9.19.1.9, 9.18.3.39, 9.16.4.19, and 102 more
- Cisco Cisco Secure Firewall Threat Defense (FTD) Software
7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.2.0, 7.0.2.1, 7.0.3, 7.2.0.1, 7.0.4, 7.2.1, 7.0.5, 7.3.0, 7.2.2, 7.2.3, 7.3.1, 7.2.4, 7.0.6, 7.2.5, 7.2.4.1, 7.3.1.1, 7.4.0, 7.0.6.1, 7.2.5.1, 7.4.1, 7.2.6, 7.0.6.2, 7.4.1.1, 7.2.7, 7.2.5.2, and 31 more
References 1
sec.cloudapps.cisco.com
Questions about CVE-2026-20349
What does this mean?
An unauthenticated remote attacker can crash and reload the device, causing a denial of service. The problem involves the SSL listen sockets that these VPN features enable.Source: sec.cloudapps.cisco.com
Am I affected, and how do I check?
Vulnerable releases of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software are affected, but only when a vulnerable configuration is enabled: SSL VPN (webvpn), IKEv2 Remote Access VPN with client services, or Zero Trust Network Access (FTD only). The facts do not list affected version numbers, so check the software version and whether these features are configured on the device.Source: sec.cloudapps.cisco.com
What should I do about it?
The facts do not name a fixed release, so no upgrade target is given here. Check Cisco's advisory for the fixed version.Source: sec.cloudapps.cisco.com
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-08-11, which means it has evidence of attacks. No public exploit code is tracked.Source: cisa.gov, cve.now feed data
What if there's no patch?
No fix is listed in the facts. Limiting exposure means disabling the affected features (SSL VPN, IKEv2 Remote Access VPN with client services, or Zero Trust Network Access on FTD) if they are not needed.Source: sec.cloudapps.cisco.com