{"id":"CVE-2026-109399","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-109399","generatedAt":"2026-10-28T05:28:22.572Z","title":"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.","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.","published":"2026-10-12T16:17:06.000Z","lastModified":"2026-10-18T12:17:05.000Z","status":"Deferred","sourceIdentifier":"disclosure@vulncheck.com","cvss":{"version":"4.0","score":9.2,"severity":"CRITICAL","vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M"},"cwe":["CWE-295"],"affected":[],"epss":{"score":0.00207,"percentile":0.10691,"date":"2026-10-27","history":[{"date":"2026-10-13","score":0.0021,"percentile":0.10409}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.21%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-12T16:17:06.000Z","detail":{"score":"9.2","severity":"CRITICAL","publishedAt":"2026-10-12T16:17:05.557Z"},"summary":"New CVE, critical severity (CVSS 9.2)."}],"references":[{"url":"https://github.com/sbabic/swupdate","source":"disclosure@vulncheck.com"},{"url":"https://github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c","source":"disclosure@vulncheck.com"},{"url":"https://github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9","source":"disclosure@vulncheck.com"},{"url":"https://groups.google.com/g/swupdate/c/dsoMcGFnEns","source":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates","source":"disclosure@vulncheck.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-109399","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}