CVE-2026-20349 — Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
CISA KEVAs of 2026-08-12, CVE-2026-20349 is a HIGH-severity vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, CVSS v3.1 8.6, EPSS 0.8% (55.7th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-08-11), with a US federal remediation deadline of 2026-08-14. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-20349, most recently “Cisco Secure Firewall ASA/FTD Zero-Day (CVE-2026-20349) Exploited for DoS via Crafted HTTP Requests to Remote Access SSL VPN”.
Last updated: 2026-08-12
What is CVE-2026-20349?
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.
The record classifies CVE-2026-20349 under weakness class CWE-244. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 32 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.6 — HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - EPSS (FIRST)
- 0.8% probability of exploitation in the next 30 days, higher than 55.7% of all scored CVEs
- CISA KEV
- Listed since 2026-08-11, federal remediation deadline 2026-08-14
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2026-08-11, last modified 2026-08-12
Is CVE-2026-20349 being exploited?
CISA added CVE-2026-20349 to the Known Exploited Vulnerabilities catalog on 2026-08-11, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-08-14 under BOD 22-01. It currently carries a trending score of 53 in the Threadlinqs vulnerability feed.
Affected products and versions
- Cisco: Secure Firewall Adaptive Security Appliance (ASA) Software, Secure Firewall Threat Defense (FTD) Software
How to fix CVE-2026-20349
Vendor advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF. Because CVE-2026-20349 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-08-14. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-20349
1 tracked threat in the Threadlinqs corpus references CVE-2026-20349, either in the campaign’s CVE list or as an indicator on the campaign record.
- Cisco Secure Firewall ASA/FTD Zero-Day (CVE-2026-20349) Exploited for DoS via Crafted HTTP Requests to Remote Access SSL VPN — HIGH · 2026-08-12
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.
Other references
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