CVE-2020-15673
📋 TL;DR
CVE-2020-15673 is a memory corruption vulnerability in Mozilla Firefox, Thunderbird, and Firefox ESR that could allow attackers to execute arbitrary code. The vulnerability stems from use-after-free memory safety bugs that can be exploited through crafted web content. Affected users include anyone running vulnerable versions of these applications.
💻 Affected Systems
- Mozilla Firefox
- Mozilla Thunderbird
- Mozilla Firefox ESR
📦 What is this software?
Firefox by Mozilla
Firefox Esr by Mozilla
Leap by Opensuse
Leap by Opensuse
Thunderbird by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the user running the vulnerable application, potentially leading to full system compromise.
Likely Case
Browser crash or denial of service, with potential for limited code execution in targeted attacks.
If Mitigated
No impact if patched versions are deployed or if vulnerable applications are not used for untrusted content.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website or opening malicious email). Memory corruption bugs require specific conditions to achieve reliable code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 81+, Thunderbird 78.3+, Firefox ESR 78.3+
Vendor Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2020-42/
Restart Required: Yes
Instructions:
1. Open the affected application. 2. Navigate to Help > About Firefox/Thunderbird. 3. Allow the application to check for and install updates. 4. Restart the application when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to prevent exploitation through web content
about:config -> javascript.enabled = false
Use alternative browser
allSwitch to a non-vulnerable browser until patches can be applied
🧯 If You Can't Patch
- Restrict access to untrusted websites and email content
- Implement application whitelisting to prevent execution of unauthorized code
🔍 How to Verify
Check if Vulnerable:
Check application version in Help > About Firefox/ThunderbirdCheck Version:
firefox --version || thunderbird --versionVerify Fix Applied:
Verify version is Firefox 81+, Thunderbird 78.3+, or Firefox ESR 78.3+📡 Detection & Monitoring
Log Indicators:
- Application crash logs with memory access violations
- Unexpected process termination
Network Indicators:
- Connections to known malicious domains preceding crashes
SIEM Query:
source="firefox.log" AND ("crash" OR "segmentation fault" OR "access violation")🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1648493%2C1660800
- https://lists.debian.org/debian-lts-announce/2020/10/msg00020.html
- https://security.gentoo.org/glsa/202010-02
- https://www.debian.org/security/2020/dsa-4770
- https://www.mozilla.org/security/advisories/mfsa2020-42/
- https://www.mozilla.org/security/advisories/mfsa2020-43/
- https://www.mozilla.org/security/advisories/mfsa2020-44/
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1648493%2C1660800
- https://lists.debian.org/debian-lts-announce/2020/10/msg00020.html
- https://security.gentoo.org/glsa/202010-02
- https://www.debian.org/security/2020/dsa-4770
- https://www.mozilla.org/security/advisories/mfsa2020-42/
- https://www.mozilla.org/security/advisories/mfsa2020-43/
- https://www.mozilla.org/security/advisories/mfsa2020-44/
