CVE-2025-6436Improper Restriction of Operations within the Bounds of a Memory Buffer in Mozilla Firefox

Severity
8.1HIGHNVD
EPSS
0.1%
top 65.73%
CISA KEV
Not in KEV
Exploit
No known exploits
Timeline
PublishedJun 24
Latest updateFeb 2

Description

Memory safety bugs present in Firefox 139 and Thunderbird 139. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitability: 2.2 | Impact: 5.9

Affected Packages3 packages

NVDmozilla/firefox< 140.0
NVDmozilla/thunderbird< 140.0
Ubuntumozilla/thunderbird< 1:140.7.1+build1-0ubuntu0.22.04.1

🔴Vulnerability Details

3
OSV
CVE-2025-6436: Memory safety bugs present in Firefox 139 and Thunderbird 1392025-06-24
GHSA
GHSA-x8w4-qgw5-r433: Memory safety bugs present in Firefox 139 and Thunderbird 1392025-06-24
CVEList
Memory safety bugs fixed in Firefox 140 and Thunderbird 1402025-06-24

📋Vendor Advisories

5
Ubuntu
Thunderbird vulnerabilities2026-02-02
Red Hat
firefox: Memory safety bugs fixed in Firefox 140 and Thunderbird 1402025-06-24
Debian
CVE-2025-6436: firefox - Memory safety bugs present in Firefox 139 and Thunderbird 139. Some of these bug...2025
Mozilla
Mozilla Foundation Security Advisory 2025-54: CVE-2025-6436
Mozilla
Mozilla Foundation Security Advisory 2025-51: CVE-2025-6436

💬Community

1
Bugzilla
CVE-2025-10158 rsync: Rsync: Out of bounds array access via negative index2025-11-18
CVE-2025-6436 — Mozilla Firefox vulnerability | cvebase