Full Report
AL26-018 - Vulnerability affecting Cisco ASA and Secure Firewall Threat Defense Software Remote Access SSL VPN - CVE-2026-20349
Analysis Summary
# Vulnerability: Cisco ASA and FTD Remote Access SSL VPN Denial of Service
## CVE Details
- **CVE ID:** CVE-2026-20349
- **CVSS Score:** High (Specific numerical score not provided in text, but categorized as High-severity)
- **CWE:** CWE-244 (Improper Clearing of Heap Memory Before Release / 'Heap Inspection')
## Affected Systems
- **Products:**
- Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- Cisco Secure Firewall Threat Defense (FTD) Software
- **Versions:** Multiple versions (Specific version table not provided in snippet; refer to Cisco Advisory)
- **Configurations:** Systems with **Remote Access SSL VPN services** enabled and accessible from the internet.
## Vulnerability Description
The vulnerability exists due to insufficient error checking when the software processes incoming HTTP requests directed at the SSL VPN service. Specifically, it involves the improper clearing of heap memory before release. This flaw allows an unauthenticated remote attacker to trigger an unexpected reload of the firewall device.
## Exploitation
- **Status:** Exploited in the wild (Confirmed by Cisco as of August 11, 2026)
- **Complexity:** Low (Inferred from the ability to trigger via crafted HTTP requests)
- **Attack Vector:** Network (Remote, unauthenticated)
## Impact
- **Confidentiality:** None (Based on typical DoS profiles)
- **Integrity:** None
- **Availability:** High (Results in device reload and Denial of Service)
## Remediation
### Patches
Cisco has released software updates to address this vulnerability. Organizations are urged to migrate to the following fixed releases or later:
- Users should consult the official Cisco Security Advisory for the specific fixed version mapping for their current ASA/FTD release train.
### Workarounds
- The provided text does not list specific workarounds. Standard practice for such vulnerabilities usually involves disabling the affected SSL VPN service if not required or restricting access via ACLs to known IP addresses until patches can be applied.
## Detection
- **Indicators of compromise:**
- Unexpected and repeated reloads of the ASA or FTD appliance.
- Presence of crafted HTTP requests in web logs or packet captures directed at the SSL VPN endpoints.
- **Detection methods and tools:**
- Monitor device crash logs for signatures related to heap memory errors or process crashes in the VPN subsystem.
- Review Cisco's AV26-807 advisory for specific telemetry or logging patterns.
## References
- Cisco Security Advisory (August 11, 2026): hxxps[://]sec[.]cloudapps[.]cisco[.]com/security/center/publicationListing[.]x
- Canadian Centre for Cyber Security Alert AL26-018: hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/al26-018-vulnerability-affecting-cisco-asa-secure-firewall-threat-defense-software-remote-access-ssl-vpn-cve-2026-20349
- MITRE CVE-2026-20349: hxxps[://]cve[.]mitre[.]org/cgi-bin/cvename[.]cgi?name=CVE-2026-20349