# CVE-2026-109399: swupdate: SWUpdate through 2026.05.1 contains an improper certificate validation vulnerability in crypto/swupdate_cms_verify_op...

CVE-2026-109399 is fixed in swupdate on 1 platform, first by DEBIAN-CVE-2026-109399, released October 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-109399
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 12, 2026

## Description

SWUpdate through 2026.05.1 contains an improper certificate validation vulnerability in crypto/swupdate_cms_verify_openssl.c that trusts untrusted X.509 certificates embedded in CMS SignedData for chain building. Attackers holding a signing key from a sibling intermediate under the same root can embed that intermediate in the signature to install malicious updates.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | swupdate Debian 12.15 (bookworm) | 2022.12+dfsg-4+deb12u3 | [DEBIAN-CVE-2026-109399](https://patchblox.com/security/data/fix/linux/debian-cve-2026-109399.md) | Oct 13, 2026 |
| Linux | swupdate Debian 14 | 2026.05+dfsg-1 | [DEBIAN-CVE-2026-109399](https://patchblox.com/security/data/fix/linux/debian-cve-2026-109399.md) | Oct 13, 2026 |

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Data as of 2026-11-09T19:38:12Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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