CVE-2024-11708: Mozilla Firefox Race Condition Vulnerability

CVE-2024-11708 Overview

CVE-2024-11708 is a data race vulnerability affecting Mozilla Firefox and Thunderbird versions prior to 133. The flaw stems from missing thread synchronization primitives when multiple threads access members of the PlaybackParams structure. Concurrent reads and writes without proper locking can result in inconsistent state and integrity impact within the media playback subsystem. The vulnerability is classified under [CWE-362] Concurrent Execution using Shared Resource with Improper Synchronization. Exploitation requires user interaction, typically by convincing a user to load a crafted web page or email containing media content.

Critical Impact
A remote attacker can trigger a data race on PlaybackParams members, potentially corrupting media state and impacting integrity within Firefox and Thunderbird prior to version 133.

Affected Products

Mozilla Firefox versions prior to 133
Mozilla Thunderbird versions prior to 133
Any downstream distributions bundling Firefox or Thunderbird before version 133

Discovery Timeline

2024-11-26 - CVE-2024-11708 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-11708

Vulnerability Analysis

The vulnerability resides in the media playback code path shared by Firefox and Thunderbird. The PlaybackParams structure holds parameters governing audio and video playback state. Multiple threads read and modify members of this structure without adequate synchronization primitives such as mutexes or atomic operations.

Because the affected code lacks proper locking, two or more threads can access the same memory concurrently. The C++ memory model treats such concurrent unsynchronized access as undefined behavior. In practice, this can lead to torn reads, stale values, or inconsistent playback state that a crafted media stream can influence.

The integrity impact stems from an attacker's ability to induce inconsistent state in the media pipeline. Availability and confidentiality are not directly affected according to the assigned CVSS vector.

Root Cause

The root cause is the absence of thread synchronization primitives protecting shared members of the PlaybackParams structure. Mozilla addressed the issue by introducing proper synchronization in the media playback code. Full technical details are tracked in Mozilla Bug Report #1922912, which remains restricted at the time of publication.

Attack Vector

Exploitation requires user interaction over the network. A user must load a crafted HTML page or email message that triggers the vulnerable media playback code path. Because Thunderbird processes HTML email content using the same rendering engine, both products share the exposure. No verified public proof-of-concept exploit is available. See the Mozilla Security Advisory MFSA-2024-63 and Mozilla Security Advisory MFSA-2024-67 for vendor guidance.

No verified exploit code is publicly available. The vulnerability mechanism is described in prose based on the Mozilla advisory content.

Detection Methods for CVE-2024-11708

Indicators of Compromise

Firefox or Thunderbird processes crashing or exhibiting inconsistent media playback behavior after loading untrusted content
Unexpected renderer process terminations logged in browser crash telemetry involving media component threads
Endpoints running Firefox or Thunderbird versions below 133 accessing untrusted media content

Detection Strategies

Inventory endpoints and identify Firefox and Thunderbird installations with versions below 133 using software asset management tools
Monitor browser crash reports and telemetry for repeated media subsystem faults that may indicate exploitation attempts
Correlate network traffic to untrusted domains serving crafted media with subsequent browser process anomalies

Monitoring Recommendations

Track Firefox and Thunderbird version deployments across managed endpoints and flag installations below 133
Alert on unexpected child process spawns or crashes from firefox.exe, thunderbird.exe, or their Linux and macOS equivalents
Log outbound connections from browser and email client processes to newly observed or low-reputation domains

How to Mitigate CVE-2024-11708

Immediate Actions Required

Upgrade Mozilla Firefox to version 133 or later on all managed endpoints
Upgrade Mozilla Thunderbird to version 133 or later on all managed endpoints
Prioritize systems that regularly process untrusted media content or external email
Verify that automatic update mechanisms are enabled and functioning across the fleet

Patch Information

Mozilla released fixed versions of Firefox and Thunderbird at version 133. Refer to Mozilla Security Advisory MFSA-2024-63 for Firefox 133 details and Mozilla Security Advisory MFSA-2024-67 for Thunderbird 133 details. Apply the vendor updates through standard patch management channels.

Workarounds

Disable autoplay and remote content loading in Thunderbird until the patch is deployed
Restrict rendering of HTML email from untrusted senders
Apply browser policies that limit media playback from untrusted origins where operationally feasible
Use content filtering at the network perimeter to block known malicious media hosts

bash

# Verify installed Firefox version on Linux endpoints
firefox --version

# Verify installed Thunderbird version on Linux endpoints
thunderbird --version

# Example: enforce minimum Firefox version via enterprise policy (policies.json)
# Place in the distribution/ directory of the Firefox installation
# {
#   "policies": {
#     "DisableAppUpdate": false,
#     "AppAutoUpdate": true
#   }
# }