CVE-2024-3854 – This vulnerability in Mozilla's JavaScript JIT ... (How to Fix)

Q: How do I fix CVE-2024-3854?

1. Open affected application. 2. Go to Help > About Firefox/Thunderbird. 3. Allow automatic update to complete. 4. Restart the application when prompted.

Q: What is the severity of CVE-2024-3854?

CVE-2024-3854 has a CVSS score of 8.8 (HIGH). This vulnerability in Mozilla's JavaScript JIT compiler incorrectly optimizes switch statements, leading to out-of-bounds memory reads. It affects Firefox, Firefox ESR, and Thunderbird users running vulnerable versions. Attackers could exploit this to read sensitive memory contents or potentially achieve remote code execution.

📋 TL;DR

This vulnerability in Mozilla's JavaScript JIT compiler incorrectly optimizes switch statements, leading to out-of-bounds memory reads. It affects Firefox, Firefox ESR, and Thunderbird users running vulnerable versions. Attackers could exploit this to read sensitive memory contents or potentially achieve remote code execution.

💻 Affected Systems

Products:

Firefox
Firefox ESR
Thunderbird

Versions: Firefox < 125, Firefox ESR < 115.10, Thunderbird < 115.10

Operating Systems: All platforms where affected versions run

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations are vulnerable. No special settings required for exploitation.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise, data theft, or installation of persistent malware.

🟠

Likely Case

Information disclosure through memory reads, potentially exposing sensitive data like passwords, cookies, or session tokens.

🟢

If Mitigated

Limited impact if sandboxing works correctly, potentially just a browser crash or denial of service.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires JavaScript execution, which is standard in web browsing. No authentication needed as it can be triggered via malicious web content.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firefox 125+, Firefox ESR 115.10+, Thunderbird 115.10+

Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2024-18/

Restart Required: Yes

Instructions:

1. Open affected application. 2. Go to Help > About Firefox/Thunderbird. 3. Allow automatic update to complete. 4. Restart the application when prompted.

🔧 Temporary Workarounds

Disable JavaScript

all

Prevents exploitation by blocking JavaScript execution, which is required to trigger the vulnerability.

Use alternative browser

all

Temporarily switch to a non-vulnerable browser until patches are applied.

🧯 If You Can't Patch

Restrict web browsing to trusted sites only
Implement network segmentation to limit browser access to sensitive systems

🔍 How to Verify

Check if Vulnerable:

Check application version in Help > About Firefox/Thunderbird. If version is below patched versions, system is vulnerable.

Check Version:

firefox --version or thunderbird --version

Verify Fix Applied:

Verify version is Firefox 125+, Firefox ESR 115.10+, or Thunderbird 115.10+ after update.

📡 Detection & Monitoring

Log Indicators:

Browser crash reports
Unexpected memory access errors in system logs

Network Indicators:

Suspicious JavaScript delivery to browsers

SIEM Query:

source="browser_logs" AND (event="crash" OR event="memory_error")

📊 Metadata

CVE ID: CVE-2024-3854

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-125

Published: April 16, 2024

Last Updated: April 1, 2025

🔗 References

https://bugzilla.mozilla.org/show_bug.cgi?id=1884552 Issue Tracking
https://lists.debian.org/debian-lts-announce/2024/04/msg00012.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2024/04/msg00013.html Mailing List,Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2024-18/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2024-19/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2024-20/ Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1884552 Issue Tracking
https://lists.debian.org/debian-lts-announce/2024/04/msg00012.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2024/04/msg00013.html Mailing List,Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2024-18/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2024-19/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2024-20/ Vendor Advisory

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🔗 Related Vulnerabilities

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