High severity · published Aug 11, 2026
CVE-2026-20349
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability
In wildKEV
8.6
CVSS
1%
EPSS
Yes
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)1.0% · higher than 63% of CVEs
Exploited in the wildYes
CISA KEVListed Aug 11, 2026
Federal remediation dueAug 14, 2026
Ransomware campaign useNot known
Affected products
Which versions
CS
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Cisco
9.16.1; 9.16.1.28; 9.16.2; 9.16.2.3; 9.16.2.7; 9.16.2.11; +34 more · source: vendor
CS
Cisco Secure Firewall Threat Defense (FTD) Software · Cisco
7.0.0; 7.0.0.1; 7.0.1; 7.0.1.1; 7.0.2; 7.2.0; +34 more · source: vendor
AS
Adaptive Security Appliance Software · Cisco
9.16.1; 9.16.1.28; 9.16.2; 9.16.2.3; 9.16.2.7; 9.16.2.11; +34 more · source: NVD
SF
Secure Firewall Threat Defense · Cisco
7.0.0; 7.0.0.1; 7.0.1; 7.0.1.1; 7.0.2; 7.0.2.1; +34 more · source: NVD
In the news
VulnerabilityCritical
U.S. CISA adds Metabase, Windows, and Cisco Secure Firewall flaws to its Known Exploited Vulnerabilities catalog
U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds Metabase, Windows, and Cisco Secure Firewall flaws to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added the following vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog: CVE-2026-20349 is a vulnerability in Cisco Secure Firewall ASA and FTD software that could allow unauthenticated, […]
Aug 13, 2026·Security Affairs
VulnerabilityHigh
Cisco fixes vulnerability exploited to DoS its firewalls (CVE-2026-20349)
A high-severity vulnerability (CVE-2026-20349) is being leveraged by attackers to temporarily interrupt the operation of Cisco firewalls, the company has confirmed. The flaw has been added to CISA’s Known Exploited Vulnerabilities catalog and needs to be remediated by US civilian federal agencies by August 14, 2026. Details about the attacks are currently under wraps. Cisco only shared that its Product Security Incident Response Team (PSIRT) became aware of active exploitation of this vulnerability in August … More → The post Cisco fixes vulnerability exploited to DoS its firewalls (CVE-2026-20349) appeared first on Help Net Security .
Aug 13, 2026·Help Net Security
VulnerabilityHigh
Cisco ASA and FTD Flaw Exploited in the Wild Can Trigger Remote DoS
Cisco has warned that a new vulnerability impacting Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software has been exploited in the wild. The high-severity flaw, tracked as CVE-2026-20349 (CVSS score: 8.6), is a case of insufficient error checking when processing HTTP requests that could allow an unauthenticated, remote attacker to trigger
Aug 12, 2026·The Hacker News
AdvisoryHigh
CISA Adds Three Known Exploited Vulnerabilities to Catalog
CISA has added three new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation.   CVE-2026-20349 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Firewall Threat Defense (FTD) Heap Inspection Vulnerability CVE-2026-68820 Microsoft Windows Ancillary Function Driver for WinSock Use-After-Free Vulnerability CVE-2026-72898 Metabase SQL Injection Vulnerability These types of vulnerabilities are a frequent attack vector for malicious cyber actors and pose significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action for lower-risk vulnerabilities. BOD 26-04 further establishes basic expectations for when agencies must check whether threat actors compromised the system before the patch was applied. While BOD 26-04 applies only to FCEB agencies, CISA encourages all organizations to adopt risk-based vulnerability management and prioritize remediation of KEV Cata...
Aug 11, 2026·CISA Advisories
VulnerabilityHigh
[CISA KEV] CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) - Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
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.
SFSecure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) CVE-2026-20349
Aug 11, 2026·CISA KEV
Affected product
CS
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Cisco
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