CVE-2020-6831
📋 TL;DR
A buffer overflow vulnerability in WebRTC's SCTP chunk parsing allows memory corruption and potentially exploitable crashes. This affects Firefox ESR versions below 68.8, Firefox below 76, and Thunderbird below 68.8.0. Attackers could exploit this to execute arbitrary code or cause denial of service.
💻 Affected Systems
- Firefox ESR
- Firefox
- Thunderbird
📦 What is this software?
Firefox by Mozilla
Firefox Esr by Mozilla
Leap by Opensuse
Thunderbird by Mozilla
Ubuntu Linux by Canonical
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 ransomware deployment.
Likely Case
Application crash (denial of service) or limited memory corruption that could be leveraged for further exploitation.
If Mitigated
Minimal impact if systems are patched, isolated, or have exploit mitigations like ASLR/DEP enabled.
🎯 Exploit Status
Proof-of-concept code is publicly available; exploitation requires tricking user to visit malicious site or open malicious content.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox ESR 68.8+, Firefox 76+, Thunderbird 68.8.0+
Vendor Advisory: https://bugzilla.mozilla.org/show_bug.cgi?id=1632241
Restart Required: Yes
Instructions:
1. Update Firefox to version 76 or later. 2. Update Firefox ESR to version 68.8 or later. 3. Update Thunderbird to version 68.8.0 or later. 4. Restart the application after updating.
🔧 Temporary Workarounds
Disable WebRTC
allTemporarily disable WebRTC functionality to prevent SCTP processing.
about:config -> media.peerconnection.enabled = false
Network Blocking
linux/windowsBlock SCTP traffic at network perimeter to prevent exploitation.
iptables -A INPUT -p sctp -j DROP
netsh advfirewall firewall add rule name="Block SCTP" dir=in action=block protocol=132
🧯 If You Can't Patch
- Isolate affected systems from untrusted networks and users.
- Implement application whitelisting to prevent unauthorized code execution.
🔍 How to Verify
Check if Vulnerable:
Check application version: Firefox: Help -> About Firefox; Thunderbird: Help -> About Thunderbird.Check Version:
firefox --version | thunderbird --versionVerify Fix Applied:
Confirm version is Firefox ESR 68.8+, Firefox 76+, or Thunderbird 68.8.0+.📡 Detection & Monitoring
Log Indicators:
- Application crash logs with WebRTC/SCTP-related modules
- Unexpected memory access violations in browser processes
Network Indicators:
- Unusual SCTP traffic to/from client systems
- Malformed SCTP packets in network captures
SIEM Query:
source="*firefox*" OR source="*thunderbird*" AND (event_type="crash" OR message="*SCTP*" OR message="*WebRTC*")🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00000.html
- http://packetstormsecurity.com/files/158480/usrsctp-Stack-Buffer-Overflow.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1632241
- https://security.gentoo.org/glsa/202005-03
- https://security.gentoo.org/glsa/202005-04
- https://usn.ubuntu.com/4373-1/
- https://www.debian.org/security/2020/dsa-4714
- https://www.mozilla.org/security/advisories/mfsa2020-16/
- https://www.mozilla.org/security/advisories/mfsa2020-17/
- https://www.mozilla.org/security/advisories/mfsa2020-18/
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00000.html
- http://packetstormsecurity.com/files/158480/usrsctp-Stack-Buffer-Overflow.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1632241
- https://security.gentoo.org/glsa/202005-03
- https://security.gentoo.org/glsa/202005-04
- https://usn.ubuntu.com/4373-1/
- https://www.debian.org/security/2020/dsa-4714
- https://www.mozilla.org/security/advisories/mfsa2020-16/
- https://www.mozilla.org/security/advisories/mfsa2020-17/
- https://www.mozilla.org/security/advisories/mfsa2020-18/
