CVE-2025-4086: Vulnerability in Mozilla Firefox
A specially crafted filename containing a large number of encoded newline characters could obscure the file's extension when displayed in the download dialog. *This bug only affects Thunderbird for Android. Other versions of Thunderbird are unaffected.*. This vulnerability was fixed in Firefox 138 and Thunderbird 138.
AI Analysis
Technical Summary
CVE-2025-4086 is a vulnerability in Thunderbird for Android where a specially crafted filename with numerous encoded newline characters can obscure the file's extension when displayed in the download dialog. This could cause users to misidentify the file type, potentially leading to unsafe handling of downloaded files. The issue does not affect other Thunderbird or Firefox versions. Mozilla fixed this vulnerability in Thunderbird 138 and Firefox 138 releases.
Potential Impact
The vulnerability could cause users to be misled about the actual file type of a downloaded file due to obscured file extensions in the download dialog. This may increase the risk of users opening malicious files under false assumptions about their content. The impact is rated moderate with confidentiality and integrity impacts but no availability impact. There is no indication of active exploitation in the wild.
Mitigation Recommendations
This vulnerability has been fixed in Thunderbird 138 and Firefox 138. Users and administrators should update affected Thunderbird for Android installations to version 138 or later to remediate this issue. No additional mitigation steps are indicated or required according to the Mozilla advisory.
CVE-2025-4086: Vulnerability in Mozilla Firefox
Description
A specially crafted filename containing a large number of encoded newline characters could obscure the file's extension when displayed in the download dialog. *This bug only affects Thunderbird for Android. Other versions of Thunderbird are unaffected.*. This vulnerability was fixed in Firefox 138 and Thunderbird 138.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2025-4086 is a vulnerability in Thunderbird for Android where a specially crafted filename with numerous encoded newline characters can obscure the file's extension when displayed in the download dialog. This could cause users to misidentify the file type, potentially leading to unsafe handling of downloaded files. The issue does not affect other Thunderbird or Firefox versions. Mozilla fixed this vulnerability in Thunderbird 138 and Firefox 138 releases.
Potential Impact
The vulnerability could cause users to be misled about the actual file type of a downloaded file due to obscured file extensions in the download dialog. This may increase the risk of users opening malicious files under false assumptions about their content. The impact is rated moderate with confidentiality and integrity impacts but no availability impact. There is no indication of active exploitation in the wild.
Mitigation Recommendations
This vulnerability has been fixed in Thunderbird 138 and Firefox 138. Users and administrators should update affected Thunderbird for Android installations to version 138 or later to remediate this issue. No additional mitigation steps are indicated or required according to the Mozilla advisory.
Technical Details
- Data Version
- 5.1
- Assigner Short Name
- mozilla
- Date Reserved
- 2025-04-29T13:13:40.209Z
- Cisa Enriched
- true
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 682d9839c4522896dcbeccd6
Added to database: 5/21/2025, 9:09:13 AM
Last enriched: 4/14/2026, 11:46:38 AM
Last updated: 5/8/2026, 4:26:26 PM
Views: 66
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.