CVE-2022-1529: Mozilla Firefox RCE Vulnerability

CVE-2022-1529 Overview

CVE-2022-1529 is a prototype pollution vulnerability in Mozilla Firefox and related products that enables attackers to execute arbitrary JavaScript code in the privileged parent process. The flaw exists in how the browser handles inter-process communication, where message contents can be exploited to perform double-indexing into a JavaScript object, ultimately allowing attacker-controlled code execution with elevated privileges.

Critical Impact

Successful exploitation allows attackers to execute arbitrary JavaScript in the privileged parent process, potentially leading to complete browser compromise, sandbox escape, and arbitrary code execution on the victim's system.

Affected Products

• Mozilla Firefox versions prior to 100.0.2
• Mozilla Firefox ESR versions prior to 91.9.1
• Mozilla Firefox for Android versions prior to 100.3.0
• Mozilla Thunderbird versions prior to 91.9.1

Discovery Timeline

• 2022-12-22 - CVE-2022-1529 published to NVD
• 2025-04-16 - Last updated in NVD database

Technical Details for CVE-2022-1529

Vulnerability Analysis

This vulnerability is classified under CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes - Prototype Pollution). The flaw resides in Mozilla's inter-process communication (IPC) mechanism, specifically in how the parent process handles messages from child processes.

The vulnerability allows an attacker to send a specially crafted message to the browser's parent process. The contents of this message are used to perform double-indexing into a JavaScript object, which creates a prototype pollution condition. Through this pollution, attackers can modify the prototype chain of JavaScript objects, injecting malicious properties that get inherited by other objects during runtime.

The attack requires user interaction (such as visiting a malicious webpage), but once triggered, the attacker gains the ability to execute JavaScript in the privileged parent process context. This is particularly dangerous because the parent process operates outside the content sandbox, meaning successful exploitation effectively bypasses Firefox's multi-process security architecture.

Root Cause

The root cause lies in insufficient validation of message contents before they are used to index into JavaScript objects. The double-indexing operation allows an attacker to access and modify the __proto__ property or constructor.prototype, enabling them to inject arbitrary properties into the Object prototype. These injected properties propagate to all objects that inherit from the polluted prototype, allowing code injection into privileged execution contexts.

Attack Vector

The attack is network-based and requires user interaction. An attacker can host malicious content on a website or inject it into a compromised legitimate site. When a victim visits the malicious page using a vulnerable Firefox version, the attacker's JavaScript code sends a crafted IPC message to the parent process. The double-indexing operation pollutes the prototype chain, and subsequent JavaScript execution in the parent process inherits the attacker's malicious code.

The exploitation chain typically involves:

1. Victim browses to attacker-controlled content
2. Malicious script crafts a message with specially formatted contents
3. Message is sent via IPC to the parent process
4. Parent process uses message contents for double-indexing
5. Prototype pollution occurs in the privileged context
6. Attacker's JavaScript executes with parent process privileges

Detection Methods for CVE-2022-1529

Indicators of Compromise

• Unusual IPC message patterns between Firefox child and parent processes
• Unexpected JavaScript execution in parent process contexts
• Signs of prototype pollution such as modified Object.prototype properties
• Anomalous browser behavior following visits to suspicious websites

Detection Strategies

• Monitor browser processes for unexpected privilege escalation or sandbox bypass attempts
• Implement endpoint detection rules for known prototype pollution patterns in JavaScript engines
• Deploy network-based detection for malicious web content targeting Firefox vulnerabilities
• Use behavioral analysis to detect abnormal inter-process communication patterns

Monitoring Recommendations

• Enable verbose logging for Firefox IPC mechanisms in enterprise environments
• Monitor for crash reports or stability issues that may indicate exploitation attempts
• Track browser version compliance across endpoints to identify vulnerable installations
• Implement web filtering to block known malicious domains exploiting this vulnerability

How to Mitigate CVE-2022-1529

Immediate Actions Required

• Update Mozilla Firefox to version 100.0.2 or later immediately
• Update Mozilla Firefox ESR to version 91.9.1 or later
• Update Mozilla Firefox for Android to version 100.3.0 or later
• Update Mozilla Thunderbird to version 91.9.1 or later
• Review and restrict access to untrusted websites until patching is complete

Patch Information

Mozilla has released security patches addressing this vulnerability. For detailed information, refer to the Mozilla Security Advisory MFSA-2022-19 and the Mozilla Bug Report #1770048.

Organizations should prioritize updating all affected Mozilla products through official channels:

• Firefox Desktop: Update via Help > About Firefox or enterprise deployment tools
• Firefox ESR: Deploy updates through enterprise management systems
• Firefox for Android: Update via Google Play Store or enterprise MDM
• Thunderbird: Update via Help > About Thunderbird

Workarounds

• Restrict browsing to trusted websites only until patches can be applied
• Consider using alternative browsers temporarily in high-security environments
• Implement network-level filtering to block known malicious content
• Enable enhanced tracking protection and strict content blocking in Firefox settings

# Check Firefox version on Linux/macOS
firefox --version

# Verify installed version meets minimum requirements
# Firefox: 100.0.2+
# Firefox ESR: 91.9.1+
# Thunderbird: 91.9.1+