# CVE-2026-77205: libreswan: Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted fro...

CVE-2026-77205 is fixed in 2 products on 1 platform, first by RHSA-2026:89923, released October 27, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-77205
- Priority: High
- CVSS: 7.5 (low)
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 5, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libreswan RHEL 10 | 5.3.3-1.el10_2 | [RHSA-2026:89923](https://patchblox.com/security/data/fix/linux/rhsa-2026-89923.md) | Oct 27, 2026 |
| Linux | libreswan almalinux 10 | 5.3.3-1.el10_2 | [ALSA-2026:89923](https://patchblox.com/security/data/fix/linux/alsa-2026-89923.md) | Nov 7, 2026 |
| Linux | libreswan ol 10 | 0:5.3.3-1.0.1.el10_2 | [ELSA-2026-89923](https://patchblox.com/security/data/fix/linux/elsa-2026-89923.md) | Nov 7, 2026 |
| Linux | libreswan rocky 10 | 0:5.3.3-1.el10_2 | [RLSA-2026:89923](https://patchblox.com/security/data/fix/linux/rlsa-2026-89923.md) | Nov 7, 2026 |
| Linux | libreswan-minimal almalinux 10 | 5.3.3-1.el10_2 | [ALSA-2026:89923](https://patchblox.com/security/data/fix/linux/alsa-2026-89923.md) | Nov 7, 2026 |
| Linux | libreswan-minimal ol 10 | 0:5.3.3-1.0.1.el10_2 | [ELSA-2026-89923](https://patchblox.com/security/data/fix/linux/elsa-2026-89923.md) | Nov 7, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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