SEPTEMBER 17, 2026
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Case File

CVE-2026-63435

MEDIUM · CVSS 5.3 EPSS 0.33% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-01 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

The Mail library for Ruby, prior to version 2.9.1, is vulnerable to improper decoding of RFC 2047 encoded-words, which can lead to discrepancies between decoded email headers and their raw values. This flaw allows for potential sender or recipient spoofing, increasing the risk of phishing attacks and authorization-check bypass. Organizations utilizing this library for email handling should prioritize upgrading to version 2.9.1 to mitigate these risks.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

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CVE
CVE-2026-63435
Severity
MEDIUM
CVSS
5.3
EPSS
0.33%

Original NVD 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.