CVE-2026-63435: CWE-436: Interpretation Conflict in mikel mail
Description
A really Ruby Mail handler. Security Fix(es): Affected versions of this package are vulnerable to Improper Validation of Syntactic Correctness of Input through `q_value_decode` and `b_value_decode` in `lib/mail/utilities.rb`. An attacker can make a display name or local part decode to a different address than intended by supplying a malformed RFC 2047 encoded-word, including one that embeds extra encoded-word markers or additional text. The decoders only matched the first encoded-word and used a greedy charset capture, so a crafted header could cause the parsed `From`, `To`, or `Reply-To` value to omit or reshuffle literal text. Applications that display, compare, or authorize based on the decoded address can then present or act on a spoofed sender or recipient address.(CVE-2026-63435)
CVSS v3.1
Score 5.3medium
Affected software
mikel
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability arises from the q_value_decode and b_value_decode functions in lib/mail/utilities.rb of the mikel mail package. These functions only match the first encoded-word and use a greedy charset capture, allowing a crafted header with extra encoded-word markers or additional text to cause the decoded display name or local part to be reshuffled or omit literal text. This can result in applications displaying, comparing, or authorizing based on a spoofed email address.
Potential Impact
The impact is limited to integrity, where an attacker can spoof email addresses by manipulating encoded-words in email headers. This could mislead applications or users relying on the decoded addresses for display or authorization decisions. There is no confidentiality or availability impact reported.
Mitigation Recommendations
A fix is available in mikel mail version 2.9.1 and later. Users should upgrade to version 2.9.1 or above to remediate this vulnerability. No additional mitigation steps are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-16T19:35:57.767Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a973451acd9273b492939ba
Added to database: 09/01/2026, 20:23:45 UTC
Last enriched: 09/25/2026, 04:45:11 UTC
Last updated: 10/17/2026, 06:48:19 UTC
Views: 97
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