Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability
Summary
| CVE | CVE-2026-20349 |
|---|---|
| State | PUBLISHED |
| Assigner | cisco |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-11 17:17:48 UTC |
| Updated | 2026-08-12 15:02:21 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 8.6 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS: 0.008740000 probability, percentile 0.558140000 (date 2026-08-14)
CISA KEV: Listed on 2026-08-11; due 2026-08-14; ransomware use Unknown
Problem Types: CWE-244 | CWE-244 Improper Clearing of Heap Memory Before Release ('Heap Inspection')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| 3.1 | CNA | CVSSV3_1 | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
ChangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CISA Known Exploited Vulnerability
| Vendor | Cisco |
|---|---|
| Product | Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) |
| Name | Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability |
| 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. |
| Notes | https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-20349 |
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.cisa.gov/known-exploited-vulnerabilities-catalog | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | www.cisa.gov | US Government Resource |
| sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd... | [email protected] | sec.cloudapps.cisco.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
| CISA Known Exploited Vulnerabilities catalog | CISA | www.cisa.gov | kev |
No vendor comments have been submitted for this CVE.
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| ADP | 2026-08-11T00:00:00.000Z | CVE-2026-20349 added to CISA KEV |
Exploits
CNA: In August 2026, the Cisco Product Security Incident Response Team (PSIRT) became aware of active exploitation of this vulnerability. Cisco strongly recommends that customers upgrade to a fixed software release to remediate this vulnerability.
There are currently no legacy QID mappings associated with this CVE.