Answer in brief
CVE-2026-63435 records a Medium severity (CVSS 5.3) vulnerability in Mail: Email address spoofing via malformed RFC 2047 encoded-words. The current sources do not mark it as known exploited. The current feed maps mikel/mail (generic), mail (rubygems), mail (rubygems). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps mikel/mail (generic), mail (rubygems), mail (rubygems). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| mikel/mailgeneric | < 2.9.1 | Not reported |
| mailrubygems | <2.9.1 | 2.9.1 |
| mailrubygems | >=0 <2.9.1 | 2.9.1 |
Published upstream
Sep 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 1, 2026
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.
Quoted source text, attributed separately from HOL analysis.