Vulnerability in Sbabic Swupdate
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.
Vulnerability class: Improper Certificate Validation
Published .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- groups.google.com/g/swupdate/c/dsoMcGFnEns (mailing-list, technical-description)
- github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9 (patch)
- github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c (technical-description)
- github.com/sbabic/swupdate (product)
- www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verificat… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-109399?
- CVE-2026-109399 is a high-severity vulnerability in Sbabic Swupdate, classified under Improper Certificate Validation. CVSS score: 8.1/10. Published 2026-10-12.
- How severe is CVE-2026-109399?
- High severity. CVSS v3 base score is 8.1 out of 10.