by Kastro
Paper/Archive/CVE-2026-109399

CVE-2026-109399

sbabic swupdate — SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates

EPSS 0.2%CVSS 9.2
critical.is priorityof 100
30
CVSS 9.2 (CNA)9.2 / 10 × 3027.6Not in CISA KEV+300.0EPSS percentile 10.8.108 × 202.2No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
swupdate≤ 2026.05.1–CNA

Scores by source

VulnCheck (CNA)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
VulnCheck (CNA)8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

writeupgroups.google.com/g/swupdate/c/dsoMcGFnEnspatchgithub.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9writeupgithub.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.crefgithub.com/sbabic/swupdatewriteupvulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates