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Known Exploited Vulnerability
8.6
HIGH CVSS 3.1
CVE-2026-20349
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability - [Actively Exploited]
Overview
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.

Details
INFO

Published Date :

Aug. 11, 2026, 5:17 p.m.

Last Modified :

Aug. 12, 2026, 5:17 a.m.

Remotely Exploit :

Yes !

Source :

[email protected]
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

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.

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.

Known Ransomware Campaign Use:

Unknown

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

Impact
Affected Products

The following products are affected by CVE-2026-20349 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Cisco adaptive_security_appliance_software
: Total Affected Vendor : 1 | Products : 1
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 134c704f-9b21-4f2e-91b3-4a467353bcc0
CVSS 3.1 HIGH [email protected]
CVSS 3.1 HIGH MITRE-CVE
Solution
Apply available software updates to fix the HTTP request error, preventing device reloads and DoS.
  • Update Cisco Secure Firewall ASA and FTD software.
  • Apply vendor-provided patches for the SSL VPN service.
  • Implement stricter HTTP request validation.
  • Monitor device logs for suspicious activity.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-20349.

URL Resource
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-20349 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-20349 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-20349 vulnerability anywhere in the article.

  • security.nl
Cisco waarschuwt voor actief misbruik van dos-lek in vpn-service firewalls

Cisco waarschuwt organisaties voor actief misbruik van een kwetsbaarheid in de vpn-service van ASA- en FTD-firewalls waardoor een denial of service ontstaat. Zo kunnen aanvallers de apparaten op afsta ... Read more

Published Date: Aug 12, 2026 (2 hours, 23 minutes ago)
  • The Hacker News
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 hig ... Read more

Published Date: Aug 12, 2026 (3 hours, 54 minutes ago)

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-20349 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Aug. 12, 2026

    Action Type Old Value New Value
    Changed SSVC {'id': 'CVE-2026-20349', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-11T19:40:06.134027Z'} {'id': 'CVE-2026-20349', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-11T00:00:00+00:00'}
  • CVE CISA KEV Update by 9119a7d8-5eab-497f-8521-727c672e3725

    Aug. 11, 2026

    Action Type Old Value New Value
    Added Date Added 2026-08-11
    Added Due Date 2026-08-11
    Added Required Action 2026-08-11
    Added Vulnerability Name 2026-08-11
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Aug. 11, 2026

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349
    Changed SSVC {'id': 'CVE-2026-20349', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-11T17:33:50.467249Z'} {'id': 'CVE-2026-20349', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-11T19:40:06.134027Z'}
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Aug. 11, 2026

    Action Type Old Value New Value
    Added SSVC {'id': 'CVE-2026-20349', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-11T17:33:50.467249Z'}
  • New CVE Received by [email protected]

    Aug. 11, 2026

    Action Type Old Value New Value
    Added Affected [{'vendor': 'Cisco', 'product': 'Cisco Secure Firewall Adaptive Security Appliance (ASA) Software', 'versions': [{'status': 'affected', 'version': '9.16.1'}, {'status': 'affected', 'version': '9.16.1.28'}, {'status': 'affected', 'version': '9.16.2'}, {'status': 'affected', 'version': '9.16.2.3'}, {'status': 'affected', 'version': '9.16.2.7'}, {'status': 'affected', 'version': '9.16.2.11'}, {'status': 'affected', 'version': '9.16.2.13'}, {'status': 'affected', 'version': '9.16.2.14'}, {'status': 'affected', 'version': '9.16.3.3'}, {'status': 'affected', 'version': '9.16.3'}, {'status': 'affected', 'version': '9.16.3.14'}, {'status': 'affected', 'version': '9.18.1'}, {'status': 'affected', 'version': '9.16.3.15'}, {'status': 'affected', 'version': '9.18.1.3'}, {'status': 'affected', 'version': '9.18.2'}, {'status': 'affected', 'version': '9.16.3.19'}, {'status': 'affected', 'version': '9.16.3.23'}, {'status': 'affected', 'version': '9.18.2.5'}, {'status': 'affected', 'version': '9.16.4'}, {'status': 'affected', 'version': '9.18.2.7'}, {'status': 'affected', 'version': '9.19.1'}, {'status': 'affected', 'version': '9.16.4.9'}, {'status': 'affected', 'version': '9.18.2.8'}, {'status': 'affected', 'version': '9.16.4.14'}, {'status': 'affected', 'version': '9.18.3'}, {'status': 'affected', 'version': '9.19.1.5'}, {'status': 'affected', 'version': '9.19.1.9'}, {'status': 'affected', 'version': '9.18.3.39'}, {'status': 'affected', 'version': '9.16.4.19'}, {'status': 'affected', 'version': '9.19.1.12'}, {'status': 'affected', 'version': '9.18.3.46'}, {'status': 'affected', 'version': '9.16.4.27'}, {'status': 'affected', 'version': '9.19.1.18'}, {'status': 'affected', 'version': '9.18.3.53'}, {'status': 'affected', 'version': '9.18.3.55'}, {'status': 'affected', 'version': '9.16.4.38'}, {'status': 'affected', 'version': '9.16.4.39'}, {'status': 'affected', 'version': '9.18.3.56'}, {'status': 'affected', 'version': '9.20.1'}, {'status': 'affected', 'version': '9.16.4.42'}, {'status': 'affected', 'version': '9.19.1.22'}, {'status': 'affected', 'version': '9.18.4'}, {'status': 'affected', 'version': '9.20.1.5'}, {'status': 'affected', 'version': '9.18.4.5'}, {'status': 'affected', 'version': '9.19.1.24'}, {'status': 'affected', 'version': '9.16.4.48'}, {'status': 'affected', 'version': '9.18.4.8'}, {'status': 'affected', 'version': '9.20.2'}, {'status': 'affected', 'version': '9.19.1.27'}, {'status': 'affected', 'version': '9.16.4.55'}, {'status': 'affected', 'version': '9.18.4.22'}, {'status': 'affected', 'version': '9.20.2.10'}, {'status': 'affected', 'version': '9.16.4.57'}, {'status': 'affected', 'version': '9.19.1.28'}, {'status': 'affected', 'version': '9.18.4.24'}, {'status': 'affected', 'version': '9.20.2.21'}, {'status': 'affected', 'version': '9.16.4.61'}, {'status': 'affected', 'version': '9.19.1.31'}, {'status': 'affected', 'version': '9.18.4.29'}, {'status': 'affected', 'version': '9.20.2.22'}, {'status': 'affected', 'version': '9.16.4.62'}, {'status': 'affected', 'version': '9.18.4.34'}, {'status': 'affected', 'version': '9.20.3'}, {'status': 'affected', 'version': '9.16.4.67'}, {'status': 'affected', 'version': '9.16.4.70'}, {'status': 'affected', 'version': '9.18.4.40'}, {'status': 'affected', 'version': '9.23.1'}, {'status': 'affected', 'version': '9.22.1.1'}, {'status': 'affected', 'version': '9.16.4.71'}, {'status': 'affected', 'version': '9.20.3.4'}, {'status': 'affected', 'version': '9.18.4.47'}, {'status': 'affected', 'version': '9.20.3.7'}, {'status': 'affected', 'version': '9.19.1.37'}, {'status': 'affected', 'version': '9.16.4.76'}, {'status': 'affected', 'version': '9.20.3.9'}, {'status': 'affected', 'version': '9.19.1.38'}, {'status': 'affected', 'version': '9.18.4.50'}, {'status': 'affected', 'version': '9.22.1.3'}, {'status': 'affected', 'version': '9.20.3.10'}, {'status': 'affected', 'version': '9.22.1.2'}, {'status': 'affected', 'version': '9.18.4.52'}, {'status': 'affected', 'version': '9.20.3.13'}, {'status': 'affected', 'version': '9.22.1.6'}, {'status': 'affected', 'version': '9.18.4.53'}, {'status': 'affected', 'version': '9.16.4.82'}, {'status': 'affected', 'version': '9.22.2'}, {'status': 'affected', 'version': '9.20.3.16'}, {'status': 'affected', 'version': '9.19.1.42'}, {'status': 'affected', 'version': '9.18.4.57'}, {'status': 'affected', 'version': '9.16.4.84'}, {'status': 'affected', 'version': '9.23.1.3'}, {'status': 'affected', 'version': '9.20.3.20'}, {'status': 'affected', 'version': '9.22.2.4'}, {'status': 'affected', 'version': '9.23.1.7'}, {'status': 'affected', 'version': '9.20.4'}, {'status': 'affected', 'version': '9.22.2.9'}, {'status': 'affected', 'version': '9.23.1.13'}, {'status': 'affected', 'version': '9.20.4.7'}, {'status': 'affected', 'version': '9.22.2.13'}, {'status': 'affected', 'version': '9.18.4.66'}, {'status': 'affected', 'version': '9.20.4.10'}, {'status': 'affected', 'version': '9.23.1.19'}, {'status': 'affected', 'version': '9.16.4.85'}, {'status': 'affected', 'version': '9.22.2.14'}, {'status': 'affected', 'version': '9.18.4.67'}, {'status': 'affected', 'version': '9.24.1'}, {'status': 'affected', 'version': '9.18.4.68'}, {'status': 'affected', 'version': '9.23.1.22'}, {'status': 'affected', 'version': '9.20.4.14'}, {'status': 'affected', 'version': '9.22.2.20'}, {'status': 'affected', 'version': '9.18.4.71'}, {'status': 'affected', 'version': '9.20.4.19'}, {'status': 'affected', 'version': '9.23.1.26'}, {'status': 'affected', 'version': '9.16.4.89'}, {'status': 'affected', 'version': '9.22.2.32'}, {'status': 'affected', 'version': '9.18.4.76'}, {'status': 'affected', 'version': '9.22.3'}, {'status': 'affected', 'version': '9.24.1.5'}, {'status': 'affected', 'version': '9.20.4.22'}, {'status': 'affected', 'version': '9.24.1.9'}, {'status': 'affected', 'version': '9.20.4.28'}, {'status': 'affected', 'version': '9.22.3.5'}, {'status': 'affected', 'version': '9.16.4.92'}, {'status': 'affected', 'version': '9.18.4.135'}, {'status': 'affected', 'version': '9.23.1.195'}, {'status': 'affected', 'version': '9.20.4.30'}, {'status': 'affected', 'version': '9.24.1.155'}, {'status': 'affected', 'version': '9.23.1.32'}, {'status': 'affected', 'version': '9.24.1.11'}, {'status': 'affected', 'version': '9.20.4.34'}, {'status': 'affected', 'version': '9.18.4.82'}, {'status': 'affected', 'version': '9.18.4.90'}, {'status': 'affected', 'version': '9.20.4.46'}], 'defaultStatus': 'unknown'}, {'vendor': 'Cisco', 'product': 'Cisco Secure Firewall Threat Defense (FTD) Software', 'versions': [{'status': 'affected', 'version': '7.0.0'}, {'status': 'affected', 'version': '7.0.0.1'}, {'status': 'affected', 'version': '7.0.1'}, {'status': 'affected', 'version': '7.0.1.1'}, {'status': 'affected', 'version': '7.0.2'}, {'status': 'affected', 'version': '7.2.0'}, {'status': 'affected', 'version': '7.0.2.1'}, {'status': 'affected', 'version': '7.0.3'}, {'status': 'affected', 'version': '7.2.0.1'}, {'status': 'affected', 'version': '7.0.4'}, {'status': 'affected', 'version': '7.2.1'}, {'status': 'affected', 'version': '7.0.5'}, {'status': 'affected', 'version': '7.3.0'}, {'status': 'affected', 'version': '7.2.2'}, {'status': 'affected', 'version': '7.2.3'}, {'status': 'affected', 'version': '7.3.1'}, {'status': 'affected', 'version': '7.2.4'}, {'status': 'affected', 'version': '7.0.6'}, {'status': 'affected', 'version': '7.2.5'}, {'status': 'affected', 'version': '7.2.4.1'}, {'status': 'affected', 'version': '7.3.1.1'}, {'status': 'affected', 'version': '7.4.0'}, {'status': 'affected', 'version': '7.0.6.1'}, {'status': 'affected', 'version': '7.2.5.1'}, {'status': 'affected', 'version': '7.4.1'}, {'status': 'affected', 'version': '7.2.6'}, {'status': 'affected', 'version': '7.0.6.2'}, {'status': 'affected', 'version': '7.4.1.1'}, {'status': 'affected', 'version': '7.2.7'}, {'status': 'affected', 'version': '7.2.5.2'}, {'status': 'affected', 'version': '7.3.1.2'}, {'status': 'affected', 'version': '7.2.8'}, {'status': 'affected', 'version': '7.6.0'}, {'status': 'affected', 'version': '7.4.2'}, {'status': 'affected', 'version': '7.2.8.1'}, {'status': 'affected', 'version': '7.0.6.3'}, {'status': 'affected', 'version': '7.4.2.1'}, {'status': 'affected', 'version': '7.2.9'}, {'status': 'affected', 'version': '7.0.7'}, {'status': 'affected', 'version': '7.7.0'}, {'status': 'affected', 'version': '7.4.2.2'}, {'status': 'affected', 'version': '7.2.10'}, {'status': 'affected', 'version': '7.6.1'}, {'status': 'affected', 'version': '7.4.2.3'}, {'status': 'affected', 'version': '7.0.8'}, {'status': 'affected', 'version': '7.6.2'}, {'status': 'affected', 'version': '7.7.10'}, {'status': 'affected', 'version': '7.7.11'}, {'status': 'affected', 'version': '7.0.8.1'}, {'status': 'affected', 'version': '7.6.2.1'}, {'status': 'affected', 'version': '7.7.10.1'}, {'status': 'affected', 'version': '7.4.2.4'}, {'status': 'affected', 'version': '7.2.10.2'}, {'status': 'affected', 'version': '7.4.3'}, {'status': 'affected', 'version': '7.6.4'}, {'status': 'affected', 'version': '10.0.0'}, {'status': 'affected', 'version': '7.4.4'}, {'status': 'affected', 'version': '7.0.9'}, {'status': 'affected', 'version': '7.2.11'}, {'status': 'affected', 'version': '7.4.7'}, {'status': 'affected', 'version': '7.4.8'}, {'status': 'affected', 'version': '7.2.12'}, {'status': 'affected', 'version': '7.7.13'}, {'status': 'affected', 'version': '10.0.2'}], 'defaultStatus': 'unknown'}]
    Added 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.
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
    Added CWE CWE-244
    Added Reference https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 8.6
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact