CVE-2024-3856
📋 TL;DR
A use-after-free vulnerability in Firefox's WebAssembly (WASM) garbage collection allows attackers to execute arbitrary code when users visit malicious websites. This affects all Firefox versions before 125. Attackers could exploit this to compromise user systems.
💻 Affected Systems
- Mozilla Firefox
📦 What is this software?
Firefox by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full system compromise, data theft, or ransomware deployment.
Likely Case
Arbitrary code execution within browser context, potentially leading to credential theft, session hijacking, or malware installation.
If Mitigated
Limited impact if browser sandboxing works correctly, potentially only browser crash or denial of service.
🎯 Exploit Status
Exploitation requires understanding of WASM garbage collection internals and memory corruption techniques.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 125
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2024-18/
Restart Required: Yes
Instructions:
1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Firefox will check for updates and install Firefox 125. 4. Restart Firefox when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allPrevents WASM execution by disabling JavaScript, but breaks most websites.
about:config → javascript.enabled = false
Disable WebAssembly
allSpecifically blocks WASM execution while keeping JavaScript enabled.
about:config → javascript.options.wasm = false
🧯 If You Can't Patch
- Restrict browser usage to trusted websites only
- Implement application whitelisting to prevent unauthorized code execution
🔍 How to Verify
Check if Vulnerable:
Check Firefox version in menu → Help → About Firefox. If version is less than 125, system is vulnerable.Check Version:
firefox --versionVerify Fix Applied:
Confirm Firefox version is 125 or higher in About Firefox dialog.📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with WASM-related stack traces
- Unexpected memory access violations in browser process
Network Indicators:
- Requests to known malicious domains hosting WASM payloads
SIEM Query:
source="firefox.logs" AND ("WASM" OR "garbage collection" OR "use-after-free") AND severity=CRITICAL