CVE-2026-109399

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 4.0

9.2CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

0.2% chance of exploitation in the next 30 days; higher than 10% of CVEs (scores of 2026-10-25)

CWE

CWE-295

Published

2026-10-12

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

References

• https://github.com/sbabic/swupdate
• https://github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c
• https://github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9
• https://groups.google.com/g/swupdate/c/dsoMcGFnEns
• https://www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates

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