What’s Vulnerable › Vulnerabilities

CVE-2026-109399: SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-12 · updated 2026-10-18
• Weakness: CWE-295

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.

Affected products

• sbabic swupdate: through 2026.05.1

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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