{"cve":"CVE-2021-4126","nvd":{"published":"2022-12-22T20:15:11.647","modified":"2026-06-17T04:19:04.697","status":"Modified","description":"When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status. This vulnerability affects Thunderbird < 91.4.1.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N","score":6.5},"cwes":[],"references":["https://bugzilla.mozilla.org/show_bug.cgi?id=1732310","https://www.mozilla.org/security/advisories/mfsa2021-55/","https://bugzilla.mozilla.org/show_bug.cgi?id=1732310","https://www.mozilla.org/security/advisories/mfsa2021-55/"],"products":["mozilla:thunderbird"],"source":"nvd","synced_at":"2026-10-19T21:37:31.370122805+00:00"},"epss":{"cve":"CVE-2021-4126","score":0.00461,"percentile":0.39977,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}