CVE-2020-12426 – CVE-2020-12426 is a memory corruption vulnerabi... (How to Fix)

Q: How do I fix CVE-2020-12426?

1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Firefox will automatically check for updates and install Firefox 78. 4. Restart Firefox when prompted.

Q: What is the severity of CVE-2020-12426?

CVE-2020-12426 has a CVSS score of 8.8 (HIGH). CVE-2020-12426 is a memory corruption vulnerability in Firefox that could allow attackers to execute arbitrary code on affected systems. The vulnerability stems from memory safety bugs that could be exploited to corrupt memory and potentially gain control of the browser. This affects all Firefox users running versions below 78.

📋 TL;DR

CVE-2020-12426 is a memory corruption vulnerability in Firefox that could allow attackers to execute arbitrary code on affected systems. The vulnerability stems from memory safety bugs that could be exploited to corrupt memory and potentially gain control of the browser. This affects all Firefox users running versions below 78.

💻 Affected Systems

Products:

Mozilla Firefox

Versions: All versions < 78

Operating Systems: Windows, Linux, macOS, Android

Default Config Vulnerable: ⚠️ Yes

Notes: All standard Firefox installations are vulnerable. No special configurations required for exploitation.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise, data theft, or ransomware deployment.

🟠

Likely Case

Browser crash or limited memory corruption leading to denial of service or information disclosure.

🟢

If Mitigated

No impact if patched to Firefox 78 or later, or if browser is isolated from untrusted content.

🌐 Internet-Facing: HIGH - Web browsers directly interact with untrusted internet content, making exploitation trivial if vulnerable version is used.

🏢 Internal Only: MEDIUM - Internal users could still be targeted via malicious internal websites or phishing emails.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Memory corruption vulnerabilities typically require some exploitation development effort, but Firefox's widespread use makes this an attractive target.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firefox 78

Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2020-24/

Restart Required: Yes

Instructions:

1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Firefox will automatically check for updates and install Firefox 78. 4. Restart Firefox when prompted.

🔧 Temporary Workarounds

Disable JavaScript

all

Temporarily disable JavaScript to reduce attack surface while waiting to patch.

about:config → javascript.enabled = false

Use Alternative Browser

all

Switch to a non-vulnerable browser until Firefox can be updated.

🧯 If You Can't Patch

Implement network segmentation to isolate vulnerable browsers from untrusted internet content
Deploy application whitelisting to prevent execution of unauthorized code

🔍 How to Verify

Check if Vulnerable:

Open Firefox → Help → About Firefox. If version is less than 78, system is vulnerable.

Check Version:

firefox --version (Linux) or check About Firefox menu

Verify Fix Applied:

After update, verify Firefox version is 78 or higher in About Firefox dialog.

📡 Detection & Monitoring

Log Indicators:

Firefox crash reports with memory corruption signatures
Unexpected process termination events

Network Indicators:

Unusual outbound connections from Firefox process
Traffic to known exploit hosting domains

SIEM Query:

source="firefox.log" AND ("crash" OR "segmentation fault" OR "memory corruption")

📊 Metadata

CVE ID: CVE-2020-12426

CVSS v3 Score: 8.8 (HIGH)

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

CWE: CWE-787

Published: July 9, 2020

Last Updated: November 21, 2024

🔗 References

http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.html Mailing List,Third Party Advisory
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1608068%2C1609951%2C1631187%2C1637682 Exploit,Issue Tracking,Patch,Vendor Advisory
https://security.gentoo.org/glsa/202007-10 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-24/ Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.html Mailing List,Third Party Advisory
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1608068%2C1609951%2C1631187%2C1637682 Exploit,Issue Tracking,Patch,Vendor Advisory
https://security.gentoo.org/glsa/202007-10 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-24/ Vendor Advisory

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2020-12426, you might also want to check these: