A recently discovered security vulnerability, CVE-2023-5168, poses a significant risk for Firefox and Thunderbird users on Windows systems. This vulnerability allows a remote attacker to potentially exploit a crash in a privileged process due to an out-of-bounds write in the FilterNodeD2D1 component of Firefox on Windows. In this post, we'll explore this vulnerability in detail, covering:

Affected Software Versions

The following versions of Firefox and Thunderbird are affected by the security vulnerability, CVE-2023-5168:

Thunderbird versions earlier than 115.3

Please note that this vulnerability only impacts Firefox on Windows. Other operating systems are not affected.

Vulnerability Description

The vulnerability is due to an out-of-bounds write in the FilterNodeD2D1 component of Firefox on Windows systems. The vulnerable component is a part of the browser's rendering engine, which is responsible for processing web pages. This engine occasionally interacts with other parts of the browser using privileged processes.

A compromised content process could have sent malicious data to FilterNodeD2D1, resulting in an out-of-bounds write. Because this component is used in a privileged process, this vulnerability may lead to a potentially exploitable crash, allowing an attacker to execute malicious code and gain control of the affected system.

Here's an example code snippet showcasing how the FilterNodeD2D1 implementation could be vulnerable to this issue:

HRESULT FilterNodeD2D1::WriteData(/*...*/)
    // ...

    // The vulnerability lies in an incorrect boundary check for the destination buffer, allowing for an out-of-bounds write.
    if (offset + length > destBufferLength)
        return E_BOUNDS; // Should be E_INVALIDARG

    // ...

Exploit Details

Details on the actual exploitation of the vulnerability are limited as the specific exploit methods have not been disclosed to protect users from potential attacks. To give an idea of how an attacker could exploit this vulnerability, below is a high-level overview:

1. A remote attacker constructs a complex web page that causes the content process to send malicious data to FilterNodeD2D1 in a privileged process, triggering an out-of-bounds write.

Mitigation Steps

To mitigate CVE-2023-5168, users should update their Firefox and Thunderbird software to the latest versions, which have patched the vulnerability. Updating the software can be done through the following steps:


- Original Mozilla Security Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2023-07/
- CVE-2023-5168 Detail: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-5168


CVE-2023-5168 is a critical security vulnerability that affects Firefox and Thunderbird on Windows systems. It is essential for users to update their software to the latest versions to mitigate this vulnerability and protect their systems from potential exploits that could lead to crashes, execution of malicious code, or control of the affected system by an attacker.


Published on: 09/27/2023 15:19:00 UTC
Last modified on: 10/10/2023 15:15:00 UTC