CVE-2026-84134: Vulnerability in Mozilla Firefox

CVE-2026-84134 is an information disclosure vulnerability categorized as 'Other issue' in the Profile Backup component of Mozilla Firefox. It was identified internally and fixed in Firefox 155 and Firefox ESR 153.2. This vulnerability is part of a broader security update addressing multiple high-impact bugs including use-after-free, sandbox escapes, and privilege escalations. The CVSS vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. However, the vendor advisory classifies this specific issue as low impact. The fixes are included in official Mozilla releases Firefox 155 and Firefox ESR 153.2.

The vulnerability could potentially lead to information disclosure through the Profile Backup component, but it is assessed as low impact by Mozilla. The overall security update including this fix addresses critical security issues with potential for memory corruption and privilege escalation. No active exploitation is known. The CVSS score of 9.8 applies to the entire batch of vulnerabilities fixed in Firefox 155, not solely to CVE-2026-84134.

Mozilla has fixed this vulnerability in Firefox 155 and Firefox ESR 153.2. Users and administrators should update to these versions or later to remediate the issue. No additional mitigation steps are required beyond applying the official updates.