CVE-2026-77205

LOW 3.7

Denial of Service via sending bogus X.509 certificates

CVSS Score

3.7

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-772
Vendor	the libreswan project
Product	libreswan
Published	Oct 13, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Affected Versions

The Libreswan Project / libreswan

5.3 ≤ 5.3.2

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

Wojciech Tatarski (TuxCare)