CVE-2026-63435
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk26th percentile - higher than 26% of all known CVEs
Summary
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.
Risk Assessment
The risk includes potential sender or recipient spoofing, which could lead to phishing or authorization bypass.
Recommendation
Update the Mail library to version 2.9.1 or later.
Other vulnerabilities in Mail
See all- CVE-2017-13874High
An issue was discovered in certain Apple products, including iOS before 11.2, related to the 'Mail' component. It might allow remote attackers to bypass an intended encryption protection mechanism by leveraging incorrect S/MIME certificate selection.
- CVE-2017-13871High
An issue was discovered in certain Apple products, including macOS before 10.13.2, related to the 'Mail' component. It allows remote attackers to read cleartext e-mail content that was intended to be protected by S/MIME encryption.
- CVE-2016-4689High
An issue was discovered in certain Apple products, including iOS before 10.2, related to the 'Mail' component. The issue involves the lack of user alerts for S/MIME email signatures using a revoked certificate.
- GHSA-mvxr-6m87-mv2qMedium
A vulnerability in the Mail library affects the q_value_decode and b_value_decode functions, which decode only the first RFC 2047 encoded-word in a string and use an overly greedy pattern to match the charset token. A crafted, malformed encoded-word embedded in an address display name or local part could cause incorrect decoding.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS