Mozilla Firefox up to 128.6/134.x Private Browsing Mode race condition

Summaryinfo

A vulnerability marked as problematic has been reported in Mozilla Firefox up to 128.6/134.x. Affected by this vulnerability is an unknown functionality of the component Private Browsing Mode. This manipulation causes race condition. This vulnerability appears as CVE-2025-1013. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 128.6/134.x. It has been declared as problematic. Affected by this vulnerability is an unknown code of the component Private Browsing Mode. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality. The summary by CVE is:

A race condition could have led to private browsing tabs being opened in normal browsing windows. This could have resulted in a potential privacy leak. This vulnerability was fixed in Firefox 135, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.

The advisory is shared at bugzilla.mozilla.org. This vulnerability is known as CVE-2025-1013 since 02/04/2025. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 04/15/2026).

The vulnerability scanner Nessus provides a plugin with the ID 215021 (Debian dsa-5858 : firefox-esr - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 128.7 or 135 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (215021). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Web Browser

Vendor

• Mozilla

Name

• Firefox

Version

• 128.0
• 128.1
• 128.2
• 128.3
• 128.4
• 128.5
• 128.6
• 134

License

• open-source

Website

• Vendor: https://www.mozilla.org/
• Product: https://www.mozilla.org/en-US/firefox/

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Discussion