CVE-2026-20249 (CVSS 8.6)

Description

A vulnerability in the certification authentication feature of Internet Key Exchange version 2 (IKEv2) 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 an affected device to reload unexpectedly. This vulnerability is due to a logic error during the certificate authentication phase of the IKEv2 connection setup. An attacker could exploit this vulnerability by attempting to establish an IKEv2 VPN connection with a crafted certificate. A successful exploit could allow the attacker to cause the IKEv2 process to crash, causing a denial of service (DoS) condition.

Is your site exposed to CVE-2026-20249?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

8.6

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0040

Probability of exploitation

0.33%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-704 CWE-704

References

Other References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ikev2cert-dos-uWyc2xtv

Frequently Asked Questions

What is CVE-2026-20249? +

A vulnerability in the certification authentication feature of Internet Key Exchange version 2 (IKEv2) 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 an affected device to reload unexpectedly. This vulnerability is due to a logic error during the certificate authentication phase of the IKEv2 connection setup. An attacker could exploit this vulnerability by attempting to establish an IKEv2 VPN connection with a crafted certificate. A successful exploit could allow the attacker to cause the IKEv2 process to crash, causing a denial of service (DoS) condition. It has a CVSS v3.1 base score of 8.6 (HIGH).

How severe is CVE-2026-20249? +

CVE-2026-20249 has a CVSS v3.1 score of 8.6 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0040, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-20249? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-54429

Polkadot Frontier is an Ethereum and EVM compatibility layer for Polkadot and Substrate. There are various account address types in …

CVE-2026-104634

Incorrect Type Conversion or Cast vulnerability in BeamMCP.Server in ScriptKittyOS beam_mcp allows an MCP client's JSON true, false and null …

CVE-2010-20115

Arcane Software’s Vermillion FTP Daemon (vftpd) versions up to and including 1.31 contains a memory corruption vulnerability triggered by a …

CVE-2024-5436 9.8

Type confusion in Snapchat LensCore could lead to denial of service or arbitrary code execution prior to version 12.88. We …

CVE-2026-58822 9.8

In multiple functions of ftsmooth.c, there is a possible memory safety issue due to improper casting. This could lead to …

CVE-2025-41646 9.8

An unauthorized remote attacker can bypass the authentication of the affected software package by misusing an incorrect type conversion. This …

CVE-2026-20249