CVE-2024-7528: Mozilla Firefox Use-After-Free Flaw

CVE-2024-7528 Overview

CVE-2024-7528 is a use-after-free vulnerability in Mozilla Firefox, Firefox ESR, and Thunderbird. The flaw stems from an incorrect interaction between the JavaScript garbage collector and the IndexedDB implementation. An attacker who convinces a user to visit a crafted web page can trigger memory corruption in the browser process. Successful exploitation may lead to arbitrary code execution within the renderer context. Mozilla addressed the issue in Firefox 129, Firefox ESR 128.1, and Thunderbird 128.1 through advisories MFSA-2024-33, MFSA-2024-35, and MFSA-2024-37.

Critical Impact

Remote attackers can trigger a use-after-free condition through crafted IndexedDB operations, potentially leading to arbitrary code execution after user interaction with a malicious page.

Affected Products

• Mozilla Firefox versions prior to 129
• Mozilla Firefox ESR versions prior to 128.1
• Mozilla Thunderbird versions prior to 128.1

Discovery Timeline

• 2024-08-06 - CVE-2024-7528 published to NVD
• 2024-08-12 - Last updated in NVD database

Technical Details for CVE-2024-7528

Vulnerability Analysis

The vulnerability is classified as a use-after-free condition [CWE-416] within the IndexedDB component of Mozilla's Gecko engine. IndexedDB is a transactional, asynchronous client-side storage API exposed to JavaScript in the browser. The flaw arises when the JavaScript garbage collector reclaims memory that the IndexedDB subsystem still references. Subsequent operations on the freed object allow an attacker to manipulate dangling pointers. This class of memory corruption is consistently exploited in browser environments to achieve renderer-level code execution.

Root Cause

The root cause lies in incorrect lifetime management between the SpiderMonkey garbage collector and native IndexedDB objects. When a JavaScript wrapper referencing an IndexedDB resource is collected at an unexpected point, the underlying C++ object can be released while still in use. Refer to Mozilla Bug Report #1895951 for the upstream technical discussion.

Attack Vector

Exploitation requires a victim to load attacker-controlled web content in a vulnerable browser. The attacker scripts a sequence of IndexedDB transactions designed to provoke garbage collection while a native handle remains live. Once the freed memory is reallocated under attacker control, the dangling reference can be used to corrupt object state. Combined with a separate sandbox escape, the flaw can lead to full compromise of the user account.

No public proof-of-concept code is available. The vulnerability mechanism is described in prose only; see the linked Mozilla advisories for vendor-confirmed technical details.

Detection Methods for CVE-2024-7528

Indicators of Compromise

• Firefox or Thunderbird process crashes with signatures consistent with heap corruption or invalid pointer dereferences in mozilla::dom::indexedDB modules.
• Unexpected renderer child process termination followed by spawning of suspicious child processes from the browser binary.
• Outbound connections from the browser process to previously unseen domains immediately after visiting a new web page.

Detection Strategies

• Inventory installed Firefox, Firefox ESR, and Thunderbird versions across the environment and flag installations below 129, 128.1, and 128.1 respectively.
• Monitor browser crash telemetry for repeated faults in IndexedDB code paths, which can indicate exploitation attempts.
• Correlate browser process anomalies with web proxy logs to identify the originating URL.

Monitoring Recommendations

• Forward endpoint process and module-load telemetry to a centralized analytics platform for retrospective hunting.
• Track child process creation chains originating from firefox.exe and thunderbird.exe for deviations from baseline.
• Alert on browser binaries writing executable files or loading unsigned DLLs after rendering untrusted content.

How to Mitigate CVE-2024-7528

Immediate Actions Required

• Upgrade Mozilla Firefox to version 129 or later on all managed endpoints.
• Upgrade Mozilla Firefox ESR to version 128.1 or later.
• Upgrade Mozilla Thunderbird to version 128.1 or later.
• Restart affected applications after patching to ensure the vulnerable code is unloaded from memory.

Patch Information

Mozilla released fixes in Firefox 129, Firefox ESR 128.1, and Thunderbird 128.1. Patch details are available in MFSA-2024-33, MFSA-2024-35, and MFSA-2024-37.

Workarounds

• Restrict browsing to trusted sites through enterprise web filtering until patches are deployed.
• Disable JavaScript on untrusted origins using enterprise policies or browser extensions where operationally feasible.
• Deploy browser isolation technology for users who must access untrusted web content during the patch window.

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

# Enterprise policy example: enforce automatic updates via policies.json
# /etc/firefox/policies/policies.json
{
  "policies": {
    "DisableAppUpdate": false,
    "AppAutoUpdate": true
  }
}