#VU108044 Improper locking in Mozilla Firefox and Firefox ESR - CVE-2025-2817

Vulnerability identifier: #VU108044

Vulnerability risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2025-2817

CWE-ID: CWE-667

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Mozilla Firefox
Client/Desktop applications / Web browsers
Firefox ESR
Client/Desktop applications / Web browsers

Vendor: Mozilla

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to improper locking mechanism in Firefox Updater. A medium-integrity user process can  interfere with the SYSTEM-level updater by manipulating the file-locking behavior by injecting code into the user-privileged process. A local user or malicious software installed on the system can bypass intended access controls, allowing SYSTEM-level file operations on paths controlled by a non-privileged user and enabling privilege escalation.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 100.0 - 137.0.2

Firefox ESR: 102.0 - 102.15.1, 115.0 - 115.22.0, 128.0 - 128.9.0

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2025-30/
https://www.mozilla.org/en-US/security/advisories/mfsa2025-28/
https://www.mozilla.org/en-US/security/advisories/mfsa2025-29/
https://bugzilla.mozilla.org/show_bug.cgi?id=1917536

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.