CVE-2025-11153 Overview
CVE-2025-11153 is a JIT (Just-In-Time) miscompilation vulnerability in the JavaScript Engine's JIT component of Mozilla Firefox. This vulnerability allows attackers to potentially manipulate the integrity of compiled JavaScript code through network-accessible vectors, which could lead to unexpected behavior or security bypasses within the browser context.
Critical Impact
JIT miscompilation vulnerabilities can allow attackers to bypass security controls and potentially achieve code execution by exploiting incorrectly compiled JavaScript code paths.
Affected Products
- Mozilla Firefox versions prior to 143.0.3
Discovery Timeline
- 2025-09-30 - CVE-2025-11153 published to NVD
- 2026-04-13 - Last updated in NVD database
Technical Details for CVE-2025-11153
Vulnerability Analysis
This vulnerability stems from a JIT miscompilation flaw within Firefox's JavaScript engine. JIT compilers optimize JavaScript code at runtime by translating frequently executed bytecode into native machine code. When the JIT compiler produces incorrect machine code due to optimization bugs or edge case handling failures, it creates a miscompilation condition that attackers can exploit.
The vulnerability is classified under CWE-94 (Improper Control of Generation of Code), indicating that the flaw allows for the generation of code that does not match the intended semantics of the original JavaScript. This type of vulnerability can lead to type confusion, incorrect bounds checking, or other security-critical operations being bypassed when specific JavaScript code patterns trigger the faulty compilation path.
Root Cause
The root cause lies in the JIT compiler's optimization routines within Firefox's JavaScript engine. During the compilation process, certain code patterns or edge cases are not correctly handled, resulting in generated machine code that deviates from the expected behavior of the source JavaScript. This miscompilation can eliminate security checks or alter data flow in ways that violate the security assumptions of the JavaScript sandbox.
Attack Vector
The vulnerability is exploitable remotely over the network without requiring user authentication or interaction. An attacker could craft a malicious webpage containing JavaScript code specifically designed to trigger the JIT miscompilation bug. When a victim visits the attacker-controlled page, the malicious JavaScript is compiled by the vulnerable JIT engine, producing incorrect machine code that the attacker can leverage to compromise integrity within the browser context.
The attack typically follows this pattern:
- The attacker identifies JavaScript code patterns that trigger the miscompilation
- Malicious code is embedded in a webpage or advertisement
- When the victim's browser JIT-compiles the code, incorrect machine code is generated
- The attacker exploits the miscompiled code to bypass security restrictions
Detection Methods for CVE-2025-11153
Indicators of Compromise
- Unusual JavaScript execution patterns or crashes in Firefox's JavaScript engine
- Unexpected browser behavior when visiting unfamiliar websites
- Browser crash reports indicating JavaScript engine faults
- Network connections to suspicious domains serving malicious JavaScript payloads
Detection Strategies
- Monitor Firefox crash reports for JavaScript engine-related crashes that may indicate exploitation attempts
- Implement network-level detection for known malicious JavaScript patterns targeting JIT vulnerabilities
- Deploy endpoint detection solutions capable of identifying anomalous browser behavior
- Review web proxy logs for connections to domains known to host browser exploits
Monitoring Recommendations
- Enable enhanced telemetry in Firefox to capture JavaScript engine anomalies
- Monitor endpoint detection and response (EDR) solutions for suspicious browser process behavior
- Implement web content filtering to block known malicious domains
- Configure SIEM rules to alert on multiple Firefox crashes from the same endpoint
How to Mitigate CVE-2025-11153
Immediate Actions Required
- Update Mozilla Firefox to version 143.0.3 or later immediately
- Enable automatic updates to ensure timely patching of future vulnerabilities
- Consider temporarily disabling JavaScript on untrusted sites until the patch is applied
- Review and apply network-level protections to block known exploit delivery vectors
Patch Information
Mozilla has addressed this vulnerability in Firefox version 143.0.3. The fix corrects the JIT compilation logic to prevent the miscompilation condition. Organizations should prioritize this update across all managed Firefox installations.
For detailed patch information, refer to the Mozilla Security Advisory MFSA-2025-80 and the Mozilla Bug Report #1987481.
Workarounds
- Disable JIT compilation by setting javascript.options.ion and javascript.options.baselinejit to false in about:config (note: this will significantly impact browser performance)
- Use alternative browsers until Firefox can be updated
- Implement strict content security policies to limit JavaScript execution from untrusted sources
- Deploy network-based web application firewalls to filter potentially malicious JavaScript
# Firefox update verification on Linux
firefox --version
# Expected output: Mozilla Firefox 143.0.3 or higher
# To temporarily disable JIT (performance impact):
# Navigate to about:config and set:
# javascript.options.ion = false
# javascript.options.baselinejit = false
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
