CVE-2024-29944: Mozilla Firefox RCE Vulnerability

CVE-2024-29944 Overview

CVE-2024-29944 is a code injection vulnerability in Mozilla Firefox that allows an attacker to inject an event handler into a privileged object, enabling arbitrary JavaScript execution in the parent process. This vulnerability specifically affects Desktop Firefox versions and does not impact mobile versions of the browser. The flaw enables attackers to bypass Firefox's security sandbox and execute malicious JavaScript code with elevated privileges in the browser's parent process.

Critical Impact

Successful exploitation allows arbitrary JavaScript execution in Firefox's privileged parent process, potentially leading to complete browser compromise with high confidentiality, integrity, and availability impact.

Affected Products

• Mozilla Firefox versions prior to 124.0.1
• Mozilla Firefox ESR versions prior to 115.9.1
• Debian Linux 10.0 (via packaged Firefox)

Discovery Timeline

• 2024-03-22 - CVE-2024-29944 published to NVD
• 2025-04-01 - Last updated in NVD database

Technical Details for CVE-2024-29944

Vulnerability Analysis

This vulnerability is classified under CWE-830 (Inclusion of Web Functionality from an Untrusted Source), indicating a fundamental issue with how Firefox handles event handlers within privileged objects. The attack requires local access but does not require user interaction or special privileges, making it particularly concerning for shared computing environments.

The core issue stems from Firefox's event handling mechanism in privileged contexts. An attacker who can inject content into the browser can leverage this flaw to attach malicious event handlers to privileged objects. When these event handlers are triggered, the injected JavaScript code executes within the parent process context, effectively bypassing Firefox's multi-process security architecture designed to isolate web content from sensitive browser functionality.

Root Cause

The vulnerability originates from insufficient validation of event handlers attached to privileged objects within Firefox's internal architecture. Firefox's privilege separation model relies on isolating web content in separate processes from the main browser process. However, the event handler injection point allows untrusted code to bridge this security boundary, enabling execution in the privileged parent process context where security restrictions are minimal.

Attack Vector

The attack vector is local, requiring the attacker to have some form of access to inject content that will be processed by Firefox. The exploitation chain involves:

1. The attacker identifies a privileged object within Firefox that accepts event handler attachment
2. A malicious event handler containing arbitrary JavaScript is injected into this privileged object
3. When the event is triggered, the JavaScript executes in the parent process with elevated privileges
4. The attacker gains the ability to perform actions with the same privileges as the Firefox parent process

Due to the sensitive nature of this vulnerability and the lack of verified proof-of-concept code, technical implementation details should be obtained from Mozilla Bug Report #1886852 once it becomes publicly accessible. The vulnerability allows bypassing Firefox's sandbox isolation, which is designed to prevent web content from accessing sensitive browser internals.

Detection Methods for CVE-2024-29944

Indicators of Compromise

• Unusual JavaScript execution patterns originating from Firefox's parent process
• Unexpected event handler registrations on privileged browser objects
• Anomalous process behavior from firefox.exe or firefox parent processes
• Signs of sandbox escape attempts or privilege boundary violations

Detection Strategies

• Monitor for Firefox versions below 124.0.1 (standard) or 115.9.1 (ESR) across managed endpoints
• Implement browser version compliance checks as part of vulnerability management programs
• Deploy endpoint detection rules to identify suspicious JavaScript execution in privileged browser contexts
• Review application logs for signs of event handler manipulation in browser internals

Monitoring Recommendations

• Enable verbose logging on Firefox deployments in high-security environments
• Integrate browser version detection into continuous vulnerability scanning workflows
• Configure SentinelOne to alert on exploitation attempts targeting browser privilege boundaries
• Monitor for post-exploitation behaviors such as credential theft or lateral movement following browser compromise

How to Mitigate CVE-2024-29944

Immediate Actions Required

• Update Mozilla Firefox to version 124.0.1 or later immediately
• Update Mozilla Firefox ESR to version 115.9.1 or later
• Conduct an inventory of all Firefox installations across the organization to identify vulnerable versions
• Prioritize updates for systems in shared computing environments or those processing sensitive data

Patch Information

Mozilla has released security patches addressing this vulnerability. The fixes are documented in the following security advisories:

• Mozilla Security Advisory MFSA-2024-15 - Addresses Firefox standard release
• Mozilla Security Advisory MFSA-2024-16 - Addresses Firefox ESR release

Debian users should apply the updates referenced in the Debian LTS Announcement for Debian Linux 10.0. Additional technical discussion is available on the Openwall OSS Security List.

Workarounds

• Consider temporarily using alternative browsers if immediate patching is not feasible
• Restrict Firefox usage to trusted content sources until patching is complete
• Implement network-level controls to limit exposure in environments where updates cannot be immediately deployed
• Deploy application whitelisting to prevent unauthorized script execution

# Verify Firefox version on Linux systems
firefox --version

# Expected output for patched versions:
# Mozilla Firefox 124.0.1 or higher (standard release)
# Mozilla Firefox 115.9.1 or higher (ESR release)

# Package managers update commands:
# Debian/Ubuntu: sudo apt update && sudo apt upgrade firefox-esr
# Fedora/RHEL: sudo dnf update firefox