CVE-2018-5095
📋 TL;DR
An integer overflow vulnerability in the Skia graphics library allows attackers to trigger use of uninitialized memory when allocating memory for edge builders on systems with at least 8 GB of RAM. This can lead to a potentially exploitable crash, potentially enabling remote code execution. Affects Thunderbird, Firefox ESR, and Firefox users on vulnerable versions.
💻 Affected Systems
- Mozilla Thunderbird
- Mozilla Firefox ESR
- Mozilla Firefox
📦 What is this software?
Firefox by Mozilla
Firefox by Mozilla
Thunderbird by Mozilla
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or installation of persistent malware.
Likely Case
Application crash (denial of service) with potential for limited code execution in browser context.
If Mitigated
No impact if patched or if system has less than 8 GB RAM.
🎯 Exploit Status
Exploitation requires triggering the integer overflow condition and leveraging uninitialized memory, which adds complexity but is feasible for skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Thunderbird 52.6, Firefox ESR 52.6, Firefox 58
Vendor Advisory: https://bugzilla.mozilla.org/show_bug.cgi?id=1418447
Restart Required: Yes
Instructions:
1. Open affected application (Thunderbird/Firefox). 2. Go to Help > About. 3. Allow automatic update to latest version. 4. Restart application when prompted.
🔧 Temporary Workarounds
Limit system memory exposure
allReduce available RAM to below 8 GB to prevent triggering the vulnerability
Disable JavaScript
allPrevent web-based exploitation by disabling JavaScript in browser settings
🧯 If You Can't Patch
- Implement network filtering to block access to untrusted websites
- Use application whitelisting to prevent execution of malicious code
🔍 How to Verify
Check if Vulnerable:
Check application version: Thunderbird < 52.6, Firefox ESR < 52.6, or Firefox < 58 on system with ≥8 GB RAMCheck Version:
On Linux: thunderbird --version or firefox --version. On Windows: Check Help > About in application.Verify Fix Applied:
Verify application version is Thunderbird ≥52.6, Firefox ESR ≥52.6, or Firefox ≥58📡 Detection & Monitoring
Log Indicators:
- Application crash logs with memory allocation errors
- Skia library related segmentation faults
Network Indicators:
- Unusual outbound connections from browser processes
- Traffic to known exploit hosting domains
SIEM Query:
source="*browser*" AND (event="crash" OR event="segfault") AND process="thunderbird" OR process="firefox"🔗 References
- http://www.securityfocus.com/bid/102783
- http://www.securitytracker.com/id/1040270
- https://access.redhat.com/errata/RHSA-2018:0122
- https://access.redhat.com/errata/RHSA-2018:0262
- https://bugzilla.mozilla.org/show_bug.cgi?id=1418447
- https://lists.debian.org/debian-lts-announce/2018/01/msg00030.html
- https://lists.debian.org/debian-lts-announce/2018/01/msg00036.html
- https://usn.ubuntu.com/3544-1/
- https://www.debian.org/security/2018/dsa-4096
- https://www.debian.org/security/2018/dsa-4102
- https://www.mozilla.org/security/advisories/mfsa2018-02/
- https://www.mozilla.org/security/advisories/mfsa2018-03/
- https://www.mozilla.org/security/advisories/mfsa2018-04/
- http://www.securityfocus.com/bid/102783
- http://www.securitytracker.com/id/1040270
- https://access.redhat.com/errata/RHSA-2018:0122
- https://access.redhat.com/errata/RHSA-2018:0262
- https://bugzilla.mozilla.org/show_bug.cgi?id=1418447
- https://lists.debian.org/debian-lts-announce/2018/01/msg00030.html
- https://lists.debian.org/debian-lts-announce/2018/01/msg00036.html
- https://usn.ubuntu.com/3544-1/
- https://www.debian.org/security/2018/dsa-4096
- https://www.debian.org/security/2018/dsa-4102
- https://www.mozilla.org/security/advisories/mfsa2018-02/
- https://www.mozilla.org/security/advisories/mfsa2018-03/
- https://www.mozilla.org/security/advisories/mfsa2018-04/
