Mikel Mail up to 2.9.0 Utilities Utilities.b_value_decode improper authorization

Summaryinfo

A vulnerability was found in Mikel Mail up to 2.9.0 and classified as problematic. This impacts the function Mail::Utilities.q_value_decode/Mail::Utilities.b_value_decode of the component Utilities. Executing a manipulation can lead to improper authorization. This vulnerability is tracked as CVE-2026-63435. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in Mikel Mail up to 2.9.0 and classified as problematic. This vulnerability affects the function Mail::Utilities.q_value_decode/Mail::Utilities.b_value_decode of the component Utilities. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-63435 since 07/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 2.9.1 eliminates this vulnerability.

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Productinfo

Vendor

• Mikel

Name

• Mail

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9.0

Website

• Product: https://github.com/mikel/mail/

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