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.
History

Wed, 02 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
First Time appeared Mikel
Mikel mail
Vendors & Products Mikel
Mikel mail

Wed, 02 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 01 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
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.
Title Mail: Email address spoofing via malformed RFC 2047 encoded-words
Weaknesses CWE-436
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-09-01T20:09:20.820Z

Updated: 2026-09-02T15:44:56.368Z

Reserved: 2026-07-16T19:35:57.767Z

Link: CVE-2026-63435

cve-icon Vulnrichment

Updated: 2026-09-02T15:44:51.475Z

cve-icon NVD

Status : Deferred

Published: 2026-09-01T21:18:35.287

Modified: 2026-09-09T21:09:13.080

Link: CVE-2026-63435

cve-icon Redhat

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