CVE-2021-23994 – This vulnerability allows attackers to exploit ... (How to Fix)

Q: How do I fix CVE-2021-23994?

1. Open browser settings 2. Go to Help > About Firefox/Thunderbird 3. Allow automatic update or download latest version from mozilla.org 4. Restart browser

Q: What is the severity of CVE-2021-23994?

CVE-2021-23994 has a CVSS score of 8.8 (HIGH). This vulnerability allows attackers to exploit uninitialized WebGL framebuffers in Mozilla browsers, leading to memory corruption and potential arbitrary code execution. It affects users of Firefox ESR before 78.10, Thunderbird before 78.10, and Firefox before 88 who visit malicious websites.

📋 TL;DR

This vulnerability allows attackers to exploit uninitialized WebGL framebuffers in Mozilla browsers, leading to memory corruption and potential arbitrary code execution. It affects users of Firefox ESR before 78.10, Thunderbird before 78.10, and Firefox before 88 who visit malicious websites.

💻 Affected Systems

Products:

Firefox ESR
Thunderbird
Firefox

Versions: Firefox ESR < 78.10, Thunderbird < 78.10, Firefox < 88

Operating Systems: Windows, Linux, macOS

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations with WebGL enabled are vulnerable. WebGL is enabled by default in affected versions.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with the privileges of the browser process, potentially leading to full system compromise.

🟠

Likely Case

Browser crash or denial of service, with potential for limited code execution in browser sandbox.

🟢

If Mitigated

Minimal impact if browsers are fully patched or WebGL is disabled.

🌐 Internet-Facing: HIGH - Exploitable via malicious websites without user interaction beyond visiting the site.

🏢 Internal Only: MEDIUM - Requires user to visit malicious internal sites or click malicious links.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires WebGL knowledge and memory corruption techniques. No public exploit code has been released.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firefox ESR 78.10+, Thunderbird 78.10+, Firefox 88+

Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2021-14/

Restart Required: Yes

Instructions:

1. Open browser settings 2. Go to Help > About Firefox/Thunderbird 3. Allow automatic update or download latest version from mozilla.org 4. Restart browser

🔧 Temporary Workarounds

Disable WebGL

all

Prevents exploitation by disabling the vulnerable WebGL component

about:config -> webgl.disabled = true

🧯 If You Can't Patch

Restrict browser usage to trusted websites only
Implement network filtering to block malicious WebGL content

🔍 How to Verify

Check if Vulnerable:

Check browser version in Help > About. If version is below patched versions, system is vulnerable.

Check Version:

firefox --version or thunderbird --version

Verify Fix Applied:

Confirm browser version is Firefox ESR 78.10+, Thunderbird 78.10+, or Firefox 88+

📡 Detection & Monitoring

Log Indicators:

Browser crash logs with WebGL context
Memory access violation errors in browser logs

Network Indicators:

Unusual WebGL resource loading patterns
Suspicious JavaScript with WebGL API calls

SIEM Query:

source="browser_logs" AND ("WebGL" OR "framebuffer") AND ("crash" OR "access violation")

📊 Metadata

CVE ID: CVE-2021-23994

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-909

Published: June 24, 2021

Last Updated: November 21, 2024

🔗 References

https://bugzilla.mozilla.org/show_bug.cgi?id=1699077 Issue Tracking,Permissions Required,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/ Release Notes,Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1699077 Issue Tracking,Permissions Required,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/ Release Notes,Vendor Advisory

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