CVE-2024-7530: Mozilla Firefox Use-After-Free Vulnerability

CVE-2024-7530 Overview

CVE-2024-7530 is a use-after-free vulnerability in Mozilla Firefox caused by incorrect interaction with the JavaScript engine's garbage collector. The flaw affects all Firefox versions prior to 129 and is tracked under [CWE-416]. Mozilla disclosed the issue in security advisory MFSA-2024-33 on August 6, 2024.

An attacker who convinces a user to visit a crafted web page can trigger memory corruption in the browser process. Successful exploitation can lead to arbitrary code execution within the renderer with the privileges of the Firefox process.

Critical Impact
Remote attackers can corrupt browser memory through a malicious web page, potentially executing arbitrary code on the target system after user interaction.

Affected Products

Mozilla Firefox versions prior to 129
All supported desktop platforms (Windows, macOS, Linux) running Firefox < 129
Downstream builds and forks based on pre-129 Firefox releases

Discovery Timeline

2024-08-06 - Mozilla publishes security advisory MFSA-2024-33 and releases Firefox 129
2024-08-06 - CVE-2024-7530 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-7530

Vulnerability Analysis

The vulnerability is a use-after-free condition arising from incorrect garbage collection (GC) interaction within Firefox's JavaScript engine. The bug allows an object to be freed while a reference to it remains reachable from executing code. Subsequent dereferences of the dangling pointer operate on memory that has already been reclaimed.

Use-after-free bugs in JavaScript engines are typically reachable from web content. An attacker controls allocation patterns, object lifetimes, and the timing of GC operations through scripted DOM and ECMAScript operations. This control allows precise heap shaping and reliable corruption primitives.

The attack requires user interaction, such as visiting an attacker-controlled page. Once triggered, the freed slot can be reclaimed with attacker-controlled data, enabling type confusion, information disclosure, or code execution in the content process.

Root Cause

The root cause is a mismatch between object lifetime tracking and the garbage collector. Specific code paths fail to register a reference with the GC or release a reference before all consumers have completed, leaving stale pointers to collected objects. Mozilla bug 1904011 tracks the underlying defect.

Attack Vector

Exploitation occurs over the network through a malicious or compromised web page. The user must load the page in a vulnerable Firefox build, satisfying the user interaction requirement. No authentication is required. See the Mozilla Security Advisory MFSA-2024-33 and Mozilla Bug Report #1904011 for technical details.

Detection Methods for CVE-2024-7530

Indicators of Compromise

Unexpected Firefox renderer (firefox.exe or content process) crashes with access violation or SIGSEGV signatures referencing the JavaScript engine
Firefox child processes spawning shells, scripting hosts, or LOLBins such as cmd.exe, powershell.exe, or bash
Outbound connections from Firefox to attacker infrastructure following visits to untrusted pages
New persistence artifacts (scheduled tasks, registry Run keys, launch agents) created by Firefox child processes

Detection Strategies

Inventory installed Firefox versions across endpoints and flag any build below 129
Hunt for browser process telemetry showing child process creation outside expected helper binaries
Correlate browser crash dumps with subsequent suspicious process or network activity on the same host
Monitor EDR telemetry for memory protection violations originating from Firefox content processes

Monitoring Recommendations

Enable browser crash reporting and forward crash metadata to centralized logging
Track Firefox version inventory continuously through software asset management
Alert on Firefox processes performing file writes to startup or autorun locations
Capture DNS and proxy logs to identify users visiting pages immediately preceding crashes

How to Mitigate CVE-2024-7530

Immediate Actions Required

Update Firefox to version 129 or later on all managed endpoints
Force-restart Firefox sessions after deployment to ensure the patched binary is loaded
Identify and remediate any extended support or downstream builds still based on pre-129 code
Restrict execution of unpatched Firefox builds through application control policies

Patch Information

Mozilla addressed the vulnerability in Firefox 129, released on August 6, 2024. The fix is documented in Mozilla Security Advisory MFSA-2024-33 and the underlying defect is tracked in Mozilla Bug Report #1904011. Upgrading to Firefox 129 or any later release remediates CVE-2024-7530.

Workarounds

Disable JavaScript on untrusted origins by setting javascript.enabled to false in about:config where feasible
Route browsing through enterprise web filtering to block known malicious domains
Use site isolation and standard-user accounts to limit blast radius if exploitation occurs
Replace vulnerable Firefox installations with the patched build rather than relying on configuration workarounds long term

bash

# Verify the installed Firefox version meets the patched baseline
firefox --version
# Expected output: Mozilla Firefox 129.0 or later