---
id: CVE-2026-109399
title: >-
  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
summary: >-
  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 sign…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-295
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T16:17:05.557'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109399'
references:
  - url: 'https://github.com/sbabic/swupdate'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9
    label: disclosure@vulncheck.com
  - url: 'https://groups.google.com/g/swupdate/c/dsoMcGFnEns'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T16:57:59.915Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.