{"cve":"CVE-2026-63435","nvd":{"published":"2026-09-01T21:18:35.287","modified":"2026-09-09T21:09:13.080","status":"Deferred","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":["CWE-436"],"references":["https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859","https://github.com/mikel/mail/pull/1664","https://github.com/mikel/mail/releases/tag/2.9.1","https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2q"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-63435","score":0.00448,"percentile":0.38964,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-mvxr-6m87-mv2q","url":"https://osv.dev/vulnerability/GHSA-mvxr-6m87-mv2q","summary":"Mail: Email address spoofing via malformed RFC 2047 encoded-words","modified":"2026-09-10T03:50:54.686601853Z","packages":[{"ecosystem":"RubyGems","name":"mail","purl":"pkg:gem/mail","ranges":["<2.9.1"],"fixed":["2.9.1"]}]}],"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."]}