CVE-2025-3031
📋 TL;DR
This vulnerability allows an attacker to read 32 bits of sensitive data from the stack in JIT-compiled JavaScript functions. It affects Firefox web browser versions before 137 and Thunderbird email client versions before 137.
💻 Affected Systems
- Mozilla Firefox
- Mozilla Thunderbird
📦 What is this software?
Firefox by Mozilla
Thunderbird by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
An attacker could read sensitive memory contents like passwords, session tokens, or encryption keys from the browser's memory space, potentially leading to account compromise or data theft.
Likely Case
An attacker could read limited memory fragments that might contain sensitive information, but would need additional vulnerabilities to chain for full exploitation.
If Mitigated
With proper controls, the impact is limited to information disclosure of small memory fragments, which may not contain useful data.
🎯 Exploit Status
Exploitation requires JavaScript execution in the browser context, which is common via malicious websites.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 137, Thunderbird 137
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2025-20/
Restart Required: Yes
Instructions:
1. Open Firefox/Thunderbird. 2. Click menu → Help → About Firefox/Thunderbird. 3. Allow automatic update to version 137 or higher. 4. Restart the application.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript execution to prevent exploitation
In Firefox: about:config → javascript.enabled = false
🧯 If You Can't Patch
- Restrict browser usage to trusted websites only
- Implement network filtering to block malicious JavaScript sources
🔍 How to Verify
Check if Vulnerable:
Check application version in Help → About Firefox/ThunderbirdCheck Version:
firefox --version or thunderbird --versionVerify Fix Applied:
Confirm version is 137 or higher in About dialog📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript execution patterns
- Memory access violations in browser logs
Network Indicators:
- Connections to known malicious domains serving JavaScript
SIEM Query:
source="firefox.log" AND "memory access" OR source="thunderbird.log" AND "JIT"