Cisco · Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD)
CVE-2026-20349
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability
What it is
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.
CISA: 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.
What to do
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Deadline for US federal agencies: August 14, 2026
More exploited flaws from Cisco
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Oct 14, 2026 | Relative Path Traversal | Secure Email Gateway | Critical 9.8 | 2.2% |
| Sep 30, 2026 | Hex Encoding | Catalyst SD-WAN Manager | Critical 9.8 | 39% |
| Sep 16, 2026 | Incorrect Use of Privileged APIs | Identity Services Engine | Critical 10.0 | 76% |
| Sep 14, 2026 | SQL Injection | Secure Email Gateway | Critical 9.8 | 30% |
| Sep 9, 2026 | Firewall Management Center Authentication Bypass Using an Alternate Path or Channel | Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management | Critical 10.0 | 88% |
| Jul 29, 2026 | Secure Firewall Management Center Use of Hard-coded Password | Secure Firewall Management Center (FMC) | Medium 5.3 | 35% |
| Jul 13, 2026 | Cross-Site Request Forgery | IOS | High 8.1 | 34% |
| Jun 25, 2026 | Server-Side Request Forgery (SSRF) | Unified Communications Manager | High 8.6 | 88% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.