{"id":"CVE-2026-63435","summary":"Mail: Email address spoofing via malformed RFC 2047 encoded-words","details":"Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.","aliases":["GHSA-mvxr-6m87-mv2q"],"modified":"2026-09-04T22:10:53.735744275Z","published":"2026-09-01T20:09:20.820Z","related":["CGA-g54w-qgw3-99m7"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-436"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63435.json"},"references":[{"type":"WEB","url":"https://github.com/mikel/mail/releases/tag/2.9.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63435.json"},{"type":"ADVISORY","url":"https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63435"},{"type":"FIX","url":"https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859"},{"type":"FIX","url":"https://github.com/mikel/mail/pull/1664"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mikel/mail","events":[{"introduced":"0"},{"fixed":"f9d59c2e447af42e2c3dec5a56b1bb25c7292859"},{"fixed":"d645d7b5b7d03218b0bc8971ef041c991a63f5f7"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"2.9.1"}]}}],"versions":["2.7.0","2.7.0.rc3","2.7.0.rc2","2.7.0.rc1","2.6.4","2.6.3","2.6.1","2.6.0","2.4.4","2.5.3","2.5.2","2.5.1","2.5.0","2.4.3","2.4.2","2.3.0","2.4.1","2.2.18","2.2.17","2.2.15","2.2.14","2.2.13","2.2.11","2.2.10","2.2.9","2.2.8","2.2.6","2.2.5.2","2.2.5.1","2.2.5","2.2.4","2.2.3","2.2.2","2.2.0","2.1.3","2.1.2","2.0.5","2.0.3"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63435.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}