Vulnerability details

CVE-2026-109399

sbabic swupdate

SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates

CVSS 4.0

9.2Critical

Official 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.

CVSS scores

Score	Version	Source	Vector
9.2Critical	4.0	CVEProject cvelistV5 (CNA) (VulnCheck)	`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`
8.1High	3.1	CVEProject cvelistV5 (CNA) (VulnCheck)	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`

Affected products

Vendor	Product	Versions	Source
sbabic	swupdate	v ≤ 2026.05.1	CVEProject cvelistV5 (CNA)

References and advisories

https://groups.google.com/g/swupdate/c/dsoMcGFnEns technical-descriptionmailing-list
https://github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9 patch
https://github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c technical-description
https://github.com/sbabic/swupdate product
https://www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates third-party-advisory

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Details

Published: 2026-10-12
Last updated: 2026-10-18
State: Published
Assigner (CNA): VulnCheck
Kolun priority: 17 · Low

Exploit prediction (EPSS)

0.2%

Probability of exploitation in 30 days

10.8%

Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable: No
Exploitation: None
Technical impact: Total

Weaknesses (CWE)

CWE-295
Improper Certificate Validation