{"id":"CVE-2026-109399","aliases":["DEBIAN-CVE-2026-109399","EUVD-2026-97496","GHSA-xf8v-f779-856c","UBUNTU-CVE-2026-109399"],"status":"published","title":"SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates","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.","severity":{"version":"4.0","score":9.2,"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00207,"percentile":0.1088,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-295"],"published":"2026-10-12T15:16:44Z","modified":"2026-10-28T11:06:30Z","fixes":[{"ecosystem":"Debian:12","package":"swupdate","fixed_in":["2022.12+dfsg-4+deb12u3"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"swupdate","fixed_in":["2026.05+dfsg-1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2022.12+dfsg-4+deb12u3"}]}],"versions":["2022.12+dfsg-4","2022.12+dfsg-4+deb12u1","2022.12+dfsg-4+deb12u1~bpo11+1","2022.12+dfsg-4+deb12u2"]},{"source":"osv","ecosystem":"Debian:14","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2026.05+dfsg-1"}]}],"versions":["2024.12.1+dfsg-3","2025.05+dfsg-1","2025.05+dfsg-2","2025.05+dfsg-2~bpo13+1","2025.05+dfsg-3","2025.05+dfsg-3~bpo13+1","2025.12+dfsg-1","2025.12+dfsg-10","2025.12+dfsg-10~bpo13+1","2025.12+dfsg-10~bpo13+2","2025.12+dfsg-2","2025.12+dfsg-2~bpo13+1","2025.12+dfsg-3","2025.12+dfsg-4","2025.12+dfsg-5","2025.12+dfsg-6","2025.12+dfsg-7","2025.12+dfsg-7~bpo13+1","2025.12+dfsg-8","2025.12+dfsg-9"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2020.11-2","2021.04-1.1","2021.04-2","2021.04-2build1","2021.11-1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2023.05+dfsg-3","2023.05+dfsg-4","2023.05+dfsg-4build1","2023.05+dfsg-5","2023.12+dfsg-1","2023.12.1+dfsg-1ubuntu1","2023.12.1+dfsg-1ubuntu4","2023.12.1+dfsg-1ubuntu5"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2025.12+dfsg-4ubuntu1","2026.05+dfsg-3ubuntu2","2026.05+dfsg-4ubuntu1","2026.05.1+dfsg-1ubuntu1","2026.05.1+git20261001+dfsg-1ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"swupdate","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2025.05+dfsg-2ubuntu1","2025.05+dfsg-3ubuntu1","2025.12+dfsg-1ubuntu1","2025.12+dfsg-2ubuntu1","2025.12+dfsg-3ubuntu1","2025.12+dfsg-4ubuntu1"]}],"products":[{"vendor":"sbabic","product":"swupdate"}],"references":[{"url":"https://groups.google.com/g/swupdate/c/dsoMcGFnEns","tags":["technical-description","mailing-list","article","report"]},{"url":"https://github.com/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9","tags":["patch","fix","report"]},{"url":"https://github.com/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c","tags":["technical-description","article","report"]},{"url":"https://github.com/sbabic/swupdate","tags":["product","package","report"]},{"url":"https://www.vulncheck.com/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates","tags":["third-party-advisory","advisory","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109399","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-xf8v-f779-856c"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109399.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-109399","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-109399","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-109399","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-109399","title":"SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates","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.","status":"published","published":"2026-10-12T15:16:44.44Z","modified":"2026-10-18T12:03:15.694Z","cvss":[{"version":"4.0","score":9.2,"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","level":"critical","assessor":"cna"},{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:20:11.581788Z"}],"euvd":[{"id":"EUVD-2026-97496","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.","status":"published","published":"2026-10-12T15:16:44Z","modified":"2026-10-18T12:03:15Z","cvss":[{"version":"4.0","score":9.2,"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","level":"critical"}],"updated_at":"2026-11-02T17:00:00.51681Z"}],"ghsa":[{"id":"GHSA-xf8v-f779-856c","title":"SWUpdate through 2026.05.1 contains an improper certificate validation vulnerability in crypto...","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.","status":"published","published":"2026-10-12T18:31:34Z","modified":"2026-10-12T18:31:35Z","cvss":[{"version":"4.0","score":9.2,"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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical"},{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T15:13:06.481163Z"}],"nvd":[{"id":"CVE-2026-109399","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.","status":"published","published":"2026-10-12T16:17:05.557Z","modified":"2026-10-18T12:17:05.22Z","cvss":[{"version":"4.0","score":9.2,"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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"},{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:12:56.310333Z"}],"osv":[{"id":"CVE-2026-109399","title":"SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates","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. 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Attackers holding a signing key from a sibling intermediate under the same root can embed that intermediate in the signature to install malicious updates.","status":"published","published":"2026-10-12T16:17:05.557Z","modified":"2026-10-27T02:00:08.061735286Z","cvss":[{"version":"4.0","score":9.2,"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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical"}],"updated_at":"2026-11-02T15:45:49.381767Z"},{"id":"UBUNTU-CVE-2026-109399","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.","status":"published","published":"2026-10-12T16:17:00Z","modified":"2026-10-17T12:59:49.369275356Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"high"},{"version":"4.0","score":9.2,"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","level":"critical"}],"updated_at":"2026-11-02T16:55:59.130573Z"}]}}