What’s Vulnerable › Vulnerabilities

CVE-2026-77205: Denial of Service via sending bogus X.509 certificates

• Severity: low (CVSS 3.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-13 · updated 2026-10-16
• Weakness: CWE-772

Description

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Affected products

• The Libreswan Project libreswan: from 5.3 through 5.3.2

References

• https://libreswan.org/security/CVE-2026-14957/CVE-2026-14957.txt
• https://libreswan.org/security/CVE-2026-77205/
• https://libreswan.org/security/CVE-2026-77205/CVE-2026-77205.txt

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