CVE-2026-84138: Vulnerability in Mozilla Firefox
Description
Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
CVSS v3.1
Score 7.5high
Affected software
Mozilla
Firefox
Mozilla
Thunderbird
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-84138 is a denial-of-service vulnerability affecting the PDF Viewer component in Mozilla Firefox. The flaw could allow an attacker to cause a denial of service, impacting the availability of the affected software. This vulnerability was addressed and fixed in Firefox 155. The CVSS v3.1 base score is 7.5, with vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating network attack vector, low attack complexity, no privileges or user interaction required, and impact limited to availability. The vendor advisory from Mozilla confirms the fix in Firefox 155 and lists this vulnerability among multiple security issues resolved in that release.
Potential Impact
The vulnerability allows an attacker to cause a denial of service in the PDF Viewer component of Firefox, which affects the availability of the browser when processing malicious PDF content. There is no impact on confidentiality or integrity. No active exploitation has been reported.
Mitigation Recommendations
Mozilla has released an official fix for this vulnerability in Firefox 155. Users and administrators should update to Firefox 155 or later to remediate this issue. No additional mitigation steps are required beyond applying the official update.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-09-01T07:25:51.081Z
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-82/","vendor":"Mozilla"}]
Threat ID: 6a96cab2acd9273b49b6858f
Added to database: 09/01/2026, 12:53:06 UTC
Last enriched: 09/07/2026, 12:59:37 UTC
Last updated: 10/17/2026, 06:48:21 UTC
Views: 63
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