Low severity · published Oct 13, 2026
CVE-2026-77205
Denial of Service via sending bogus X.509 certificates
3.7
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 8% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
libreswan · The Libreswan Project
5.3 through 5.3.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77205
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77205
vendor-advisory
https://libreswan.org/security/CVE-2026-77205/CVE-2026-77205.txt
patch
https://libreswan.org/security/CVE-2026-77205/
related
https://libreswan.org/security/CVE-2026-14957/CVE-2026-14957.txt
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