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A high-severity vulnerability, CVE-2025-4918, has been identified in Mozilla Firefox. This flaw, demonstrated during Pwn2Own Berlin 2025, abuses JavaScript Promise resolution logic to trigger out-of-bounds memory access, potentially leading to arbitrary code execution within the browser sandbox.
Why It Matters:
- Arbitrary code execution in the browser process.
- Memory corruption leading to sensitive data leakage.
Recommended Actions:
- Update Firefox to version 138.0.4 or later (or ESR 115.23.1 / ESR 128.10.1).
- Disable JIT engines if patching isn’t immediately possible.
You Should Know:
Detection & Remediation Scripts
- Detection Script: https://lnkd.in/dxj_hjxT
- Remediation Script: https://lnkd.in/dfNv4mKp
Manual Verification & Mitigation Steps
1. Check Firefox Version (Linux/Windows/macOS):
firefox --version
2. Force Update Firefox (Linux):
sudo apt update && sudo apt upgrade firefox -y
3. Disable JIT Compilation (Temporary Workaround):
- Open Firefox and navigate to:
about:config
- Search for:
javascript.options.jit.content
- Set to
false.
4. Verify Memory Corruption Protections (Linux):
checksec --file=/usr/bin/firefox
5. Monitor Firefox Processes for Exploitation Attempts (Linux):
ps aux | grep firefox | grep -i suspicious_script
6. Windows PowerShell Check for Firefox Updates:
Get-WmiObject -Class Win32_Product | Where-Object {$_.Name -like "Firefox"} | Select-Object Name, Version
7. macOS Terminal Firefox Version Check:
/Applications/Firefox.app/Contents/MacOS/firefox --version
8. Check Active Firefox Extensions (Potential Exploit Vector):
ls ~/.mozilla/extensions/
What Undercode Say:
This vulnerability highlights the persistent risks of memory corruption flaws in widely used browsers. Immediate patching is critical, but defenders should also:
– Monitor process behavior for unusual memory access patterns.
– Enforce strict JavaScript execution policies in enterprise environments.
– Use exploit mitigation tools like ASLR (Address Space Layout Randomization) and Control Flow Integrity (CFI).
Expected Output:
- Firefox version 138.0.4 or later installed.
- JIT engines disabled if unpatched.
- No signs of unexpected memory access in Firefox processes.
Prediction:
- Increased exploitation attempts in the wild within 30 days.
- More browser-based memory corruption exploits leveraging JavaScript engines.
Relevant URLs:
References:
Reported By: Roicohen Vrx – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
