CVE-2020-15683 – This CVE describes memory safety bugs in Firefo... (How to Fix)

Q: How do I fix CVE-2020-15683?

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

Q: What is the severity of CVE-2020-15683?

CVE-2020-15683 has a CVSS score of 9.8 (CRITICAL). This CVE describes memory safety bugs in Firefox and Thunderbird that could lead to memory corruption. With sufficient effort, attackers could exploit these vulnerabilities to execute arbitrary code on affected systems. The vulnerability impacts Firefox ESR versions below 78.4, Firefox versions below 82, and Thunderbird versions below 78.4.

📋 TL;DR

This CVE describes memory safety bugs in Firefox and Thunderbird that could lead to memory corruption. With sufficient effort, attackers could exploit these vulnerabilities to execute arbitrary code on affected systems. The vulnerability impacts Firefox ESR versions below 78.4, Firefox versions below 82, and Thunderbird versions below 78.4.

💻 Affected Systems

Products:

Mozilla Firefox
Mozilla Firefox ESR
Mozilla Thunderbird

Versions: Firefox ESR < 78.4, Firefox < 82, Thunderbird < 78.4

Operating Systems: All platforms supported by affected software

Default Config Vulnerable: ⚠️ Yes

Notes: All standard installations are vulnerable. No special configuration 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 crashes, denial of service, or limited code execution within browser sandbox.

🟢

If Mitigated

No impact if systems are patched or isolated from untrusted content.

🌐 Internet-Facing: HIGH - Web browsers directly interact with untrusted internet content.

🏢 Internal Only: MEDIUM - Risk exists if users access malicious internal web content or email.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Memory corruption vulnerabilities require specific conditions to achieve reliable exploitation, but browser exposure to untrusted content makes attacks feasible.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firefox ESR 78.4+, Firefox 82+, Thunderbird 78.4+

Vendor Advisory: https://www.mozilla.org/en-US/security/advisories/

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable JavaScript

all

Reduces attack surface by disabling JavaScript execution, though this breaks most web functionality.

about:config > javascript.enabled = false

Use Content Security Policy

all

Implement CSP headers to restrict script execution from untrusted sources.

Content-Security-Policy: script-src 'self'

🧯 If You Can't Patch

Restrict browser usage to trusted websites only
Implement network segmentation to isolate vulnerable browsers from critical systems

🔍 How to Verify

Check if Vulnerable:

Check browser version in Help > About Firefox/Thunderbird. Compare against affected versions.

Check Version:

firefox --version || thunderbird --version

Verify Fix Applied:

Confirm version is Firefox ESR 78.4+, Firefox 82+, or Thunderbird 78.4+ after update.

📡 Detection & Monitoring

Log Indicators:

Browser crash reports with memory access violations
Unexpected browser process termination

Network Indicators:

Unusual outbound connections from browser processes
Traffic to known exploit hosting domains

SIEM Query:

process_name IN ('firefox.exe', 'thunderbird.exe') AND event_id IN (1000, 1001) AND description CONTAINS 'ACCESS_VIOLATION'

📊 Metadata

CVE ID: CVE-2020-15683

CVSS v3 Score: 9.8 (CRITICAL)

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

CWE: CWE-416

Published: October 22, 2020

Last Updated: November 21, 2024

🔗 References

http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00057.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00062.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html Mailing List,Third Party Advisory
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1576843%2C1656987%2C1660954%2C1662760%2C1663439%2C1666140 Broken Link,Issue Tracking,Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00027.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202010-08 Third Party Advisory
https://www.debian.org/security/2020/dsa-4780 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-45/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-46/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-47/ Release Notes,Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00057.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00062.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html Mailing List,Third Party Advisory
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1576843%2C1656987%2C1660954%2C1662760%2C1663439%2C1666140 Broken Link,Issue Tracking,Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00027.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202010-08 Third Party Advisory
https://www.debian.org/security/2020/dsa-4780 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-45/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-46/ Release Notes,Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-47/ Release Notes,Vendor Advisory

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