CVEs / CVE-2026-20349
CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
- Known exploited in the CISA KEV catalog since 11 Aug 2026
- high 8.6 CVSS 3.1 (from the CNA)
- EPSS 1.01% chance of exploitation in the next 30 days, higher than 63% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.1 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.1.28 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2.3 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2.7 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2.11 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2.13 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.2.14 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3.3 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3.14 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.1 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3.15 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.1.3 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.2 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3.19 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.3.23 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.2.5 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.4 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.2.7 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.19.1 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.4.9 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.2.8 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.4.14 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.3 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.19.1.5 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.4.18 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.19.1.9 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.18.3.39 | — |
| Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.16.4.19 | — |
Exploitation
| In CISA KEV since | 11 Aug 2026 |
|---|---|
| Due date for US federal agencies | 14 Aug 2026 |
| Used in ransomware campaigns | Unknown |
| Required action | 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. |
Severity
| CVSS 3.1 | 8.6 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-244 |
References
- CVE-2026-20349 on NVD
- CVE-2026-20349 in the CISA KEV catalog
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.