CVE-2023-29531: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2023-29531 Overview

CVE-2023-29531 is an out-of-bounds memory access vulnerability in the WebGL APIs of Mozilla Firefox and Thunderbird on macOS. An attacker can trigger memory corruption through crafted WebGL content, resulting in a potentially exploitable crash. The flaw is classified as CWE-787 (Out-of-Bounds Write) and affects Firefox versions prior to 112, Firefox ESR before 102.10, and Thunderbird before 102.10. Only macOS builds are affected; other operating systems are not impacted. Mozilla addressed the issue across advisories MFSA-2023-13, MFSA-2023-14, and MFSA-2023-15.

Critical Impact
Remote attackers can trigger memory corruption through WebGL content on macOS, enabling a potentially exploitable crash that may lead to arbitrary code execution within the browser process.

Affected Products

Mozilla Firefox < 112 (macOS)
Mozilla Firefox ESR < 102.10 (macOS)
Mozilla Thunderbird < 102.10 (macOS)

Discovery Timeline

2023-06-19 - CVE-2023-29531 published to NVD
2024-12-11 - Last updated in NVD database

Technical Details for CVE-2023-29531

Vulnerability Analysis

The vulnerability resides in how Firefox and Thunderbird handle WebGL API calls on macOS. WebGL exposes a low-level graphics interface to web content, allowing JavaScript code to drive the underlying GPU pipeline. When the affected versions process specific WebGL operations, the rendering code performs memory accesses outside the bounds of allocated buffers. This out-of-bounds write corrupts adjacent memory regions and can destabilize the browser process. Because the issue is reachable from any web page rendered in the browser or any HTML email parsed by Thunderbird, the attack surface includes routine browsing and message preview scenarios.

Root Cause

The root cause is improper boundary handling in the macOS-specific WebGL code paths, mapped to CWE-787 Out-of-Bounds Write. Validation logic fails to confirm that the index or pointer used during a WebGL operation stays within the allocated buffer. Because the bug is platform-specific, it likely involves the macOS graphics backend or driver interaction layer rather than cross-platform Gecko code.

Attack Vector

Exploitation requires a victim running an affected build on macOS to render attacker-controlled content. A remote attacker hosts a malicious page that issues WebGL calls designed to trigger the boundary violation. In Thunderbird, an HTML email containing remote content can reach the same code path. No authentication or user interaction beyond loading the content is required. Successful exploitation produces memory corruption that Mozilla describes as a potentially exploitable crash, which an attacker may leverage for code execution within the renderer.

The vulnerability manifests inside the WebGL command processing routines on macOS. Refer to Mozilla Bug Report #1794292 and Mozilla Security Advisory MFSA-2023-13 for additional technical context.

Detection Methods for CVE-2023-29531

Indicators of Compromise

Unexpected Firefox or Thunderbird crash reports on macOS endpoints referencing WebGL or GPU process faults.
Browser process spawning unusual child processes immediately following a page load that invokes WebGL.
macOS crash logs in ~/Library/Logs/DiagnosticReports/ containing Firefox or Thunderbird entries with memory access violation signatures.

Detection Strategies

Inventory installed Firefox, Firefox ESR, and Thunderbird versions on macOS hosts and flag builds below 112, 102.10, and 102.10 respectively.
Monitor endpoint telemetry for anomalous behavior originating from firefox or thunderbird processes, including unexpected memory regions marked executable.
Correlate browser crash events with outbound network connections to recently observed or low-reputation domains.

Monitoring Recommendations

Forward macOS unified logs and ReportCrash artifacts to a centralized analytics platform for retrospective hunting.
Track WebGL feature usage on managed endpoints through enterprise browser policies where supported.
Alert on persistence mechanisms or LaunchAgent creations occurring shortly after a Firefox or Thunderbird crash.

How to Mitigate CVE-2023-29531

Immediate Actions Required

Update Firefox to version 112 or later on all macOS endpoints.
Update Firefox ESR to 102.10 or later for managed deployments requiring the extended support channel.
Update Thunderbird to 102.10 or later, and restart the client to ensure the patched binary is loaded.
Validate version compliance through endpoint management tooling and remediate non-compliant hosts.

Patch Information

Mozilla released fixes in Firefox 112, Firefox ESR 102.10, and Thunderbird 102.10. Patch details are documented in Mozilla Security Advisory MFSA-2023-13, Mozilla Security Advisory MFSA-2023-14, and Mozilla Security Advisory MFSA-2023-15. The associated upstream tracking is available in Mozilla Bug Report #1794292.

Workarounds

Disable WebGL in Firefox by setting webgl.disabled to true in about:config until the update is applied.
Block remote content rendering in Thunderbird and disable JavaScript execution in mail to reduce exposure.
Restrict outbound access from macOS endpoints to untrusted sites through web filtering while patching is in progress.

bash

# Configuration example: enforce WebGL disable via Firefox enterprise policy on macOS
# /Library/Application Support/Mozilla/policies.json
{
  "policies": {
    "Preferences": {
      "webgl.disabled": {
        "Value": true,
        "Status": "locked"
      }
    }
  }
}