CVE-2020-12388 – This vulnerability allows attackers to escape F... (How to Fix)

Q: How do I fix CVE-2020-12388?

1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Allow automatic update to Firefox 76 or later. 4. Restart Firefox when prompted.

Q: What is the severity of CVE-2020-12388?

CVE-2020-12388 has a CVSS score of 10.0 (CRITICAL). This vulnerability allows attackers to escape Firefox's content process sandbox on Windows systems, potentially gaining elevated privileges or executing arbitrary code. It affects Firefox versions below 76 and Firefox ESR versions below 68.8, specifically on Windows operating systems.

📋 TL;DR

This vulnerability allows attackers to escape Firefox's content process sandbox on Windows systems, potentially gaining elevated privileges or executing arbitrary code. It affects Firefox versions below 76 and Firefox ESR versions below 68.8, specifically on Windows operating systems.

💻 Affected Systems

Products:

Mozilla Firefox
Mozilla Firefox ESR

Versions: Firefox < 76, Firefox ESR < 68.8

Operating Systems: Windows

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects Windows operating systems due to Windows-specific DACL (Discretionary Access Control List) implementation.

📦 What is this software?

Firefox by Mozilla

View all CVEs affecting Firefox →

Firefox Esr by Mozilla

View all CVEs affecting Firefox Esr →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise via sandbox escape leading to arbitrary code execution with SYSTEM privileges.

🟠

Likely Case

Local privilege escalation allowing attackers to bypass browser security controls and access sensitive system resources.

🟢

If Mitigated

Limited impact if sandbox remains intact; browser crashes or denial of service.

🌐 Internet-Facing: MEDIUM - Requires user interaction (visiting malicious site) but can lead to system compromise.

🏢 Internal Only: MEDIUM - Same exploitation path as internet-facing, but attacker needs initial access to internal network.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploit requires user to visit malicious website; public proof-of-concept available via Packet Storm Security.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firefox 76, Firefox ESR 68.8

Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2020-16/

Restart Required: Yes

Instructions:

1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Allow automatic update to Firefox 76 or later. 4. Restart Firefox when prompted.

🔧 Temporary Workarounds

Disable JavaScript

all

Temporarily disable JavaScript to prevent exploitation via malicious websites.

about:config → javascript.enabled = false

Use Alternative Browser

all

Switch to updated or alternative browser until Firefox is patched.

🧯 If You Can't Patch

Restrict user access to untrusted websites via web filtering/proxy.
Implement application whitelisting to prevent unauthorized code execution.

🔍 How to Verify

Check if Vulnerable:

Check Firefox version: about:support → Application Basics → Version. If version is <76 (or <68.8 for ESR) on Windows, system is vulnerable.

Check Version:

firefox --version

Verify Fix Applied:

Verify Firefox version is ≥76 (or ≥68.8 for ESR) after update.

📡 Detection & Monitoring

Log Indicators:

Unusual process creation from Firefox content processes
Access violations in Windows security logs

Network Indicators:

Connections to known malicious domains from Firefox processes

SIEM Query:

Process Creation where Parent Process Name contains 'firefox.exe' and Command Line contains unusual arguments

📊 Metadata

CVE ID: CVE-2020-12388

CVSS v3 Score: 10.0 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CWE: CWE-20

Published: May 26, 2020

Last Updated: November 21, 2024

🔗 References

http://packetstormsecurity.com/files/157860/Firefox-Default-Content-Process-DACL-Sandbox-Escape.html Third Party Advisory,VDB Entry
https://bugzilla.mozilla.org/show_bug.cgi?id=1618911 Issue Tracking,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-16/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-17/ Vendor Advisory
http://packetstormsecurity.com/files/157860/Firefox-Default-Content-Process-DACL-Sandbox-Escape.html Third Party Advisory,VDB Entry
https://bugzilla.mozilla.org/show_bug.cgi?id=1618911 Issue Tracking,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-16/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-17/ Vendor Advisory

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🔗 Related Vulnerabilities

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