Cisco fixes vulnerability exploited to DoS its firewalls (CVE-2026-20349)
Cisco patches CVE-2026-20349, a high-severity unauthenticated DoS in ASA and FTD VPN services now added to CISA's KEV.
CVE-2026-20349 affects the Remote Access SSL VPN service in Cisco Secure Firewall ASA and FTD software, where specially crafted unauthenticated HTTP requests can cause appliances to reload, creating a denial of service. Cisco confirmed active exploitation observed in August 2026 and released hot fixes for ASA versions 9.16 through 9.24 and FTD versions 7.0 through 10.0. The flaw was added to CISA's Known Exploited Vulnerabilities catalog with a remediation deadline of August 14, 2026 for US civilian federal agencies. No workarounds or indicators of compromise are available.
- Affects IKEv2 Remote Access VPN, SSL VPN and ZTNA features when SSL listen sockets are active
- Unauthenticated crafted HTTP requests cause unexpected appliance reloads and DoS
- Hot fixes cover ASA 9.16-9.24 and FTD 7.0-10.0; no workarounds available
- KEV remediation deadline for US civilian federal agencies is August 14, 2026
- CVEs
- CVE-2026-20349
- Countries
- United States
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-20349 | Unauthenticated Remote DoS in Cisco ASA/FTD SSL VPN Service | 8.6 | 1% | KEVPoC | KEV |
From the original article
1 min read at helpnetsecurity.com
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.
By @zeljkazorz · helpnetsecurity.com
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.