Mail is an internet library for Ruby designed to handle email generation, parsing, and sending

Overview

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.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Package advisory (CVE-2026-63435)

Affected packages:

• mail < 2.9.1

Patched in:

• mail 2.9.1

Source: https://github.com/advisories/GHSA-mvxr-6m87-mv2q

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat 3scale API Management Platform 2 · no fix planned: Red Hat 3scale API Management Platform 2 · updated 2026-10-04 · vex