CVE-2020-12066 – CVE-2020-12066 is a denial-of-service vulnerabi... (How to Fix)

Q: What is the severity of CVE-2020-12066?

CVE-2020-12066 has a CVSS score of 7.5 (HIGH). CVE-2020-12066 is a denial-of-service vulnerability in Teeworlds game servers where remote attackers can send specially crafted messages to crash the server. This affects Teeworlds 0.7.x servers before version 0.7.5. Anyone running a vulnerable Teeworlds server is at risk of service disruption.

📋 TL;DR

CVE-2020-12066 is a denial-of-service vulnerability in Teeworlds game servers where remote attackers can send specially crafted messages to crash the server. This affects Teeworlds 0.7.x servers before version 0.7.5. Anyone running a vulnerable Teeworlds server is at risk of service disruption.

💻 Affected Systems

Products:

Teeworlds

Versions: 0.7.0 through 0.7.4

Operating Systems: Linux, Windows, macOS

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects Teeworlds servers, not clients. All default configurations are vulnerable.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Server crashes and becomes unavailable to all players, requiring manual restart and causing extended downtime.

🟠

Likely Case

Server crashes and requires restart, disrupting gameplay sessions and potentially causing data loss for ongoing games.

🟢

If Mitigated

Server remains operational with proper patching or workarounds in place.

🌐 Internet-Facing: HIGH - Teeworlds servers are typically internet-facing game servers accessible to any player.

🏢 Internal Only: LOW - Teeworlds is primarily deployed as internet-facing game servers, not internal enterprise applications.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

The vulnerability is in CServer::SendMsg function and requires sending a specific message to trigger the crash. Exploit code has been publicly discussed in security advisories.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 0.7.5

Vendor Advisory: https://github.com/teeworlds/teeworlds/commit/c68402fa7e279d42886d5951d1ea8ac2facc1ea5

Restart Required: Yes

Instructions:

1. Download Teeworlds 0.7.5 or later from official sources. 2. Stop the vulnerable server. 3. Replace the server binary with the patched version. 4. Restart the server.

🔧 Temporary Workarounds

Network Filtering

all

Block or filter malicious messages at network level using firewall rules or IDS/IPS systems.

Server Restart Automation

linux

Implement automatic restart scripts to minimize downtime if server crashes.

#!/bin/bash
while true; do
  ./teeworlds_srv
  sleep 5
done

🧯 If You Can't Patch

Implement network monitoring to detect and block attack attempts
Use rate limiting to restrict message frequency from individual clients

🔍 How to Verify

Check if Vulnerable:

Check Teeworlds server version. If version is 0.7.0 through 0.7.4, it is vulnerable.

Check Version:

./teeworlds_srv --version

Verify Fix Applied:

Verify server is running version 0.7.5 or later and test server stability under normal load.

📡 Detection & Monitoring

Log Indicators:

Server crash logs
Abnormal termination messages
Segmentation fault errors

Network Indicators:

Sudden drop in server connections
Specific message patterns causing crashes

SIEM Query:

source="teeworlds.log" AND ("crash" OR "segmentation fault" OR "abnormal termination")

📊 Metadata

CVE ID: CVE-2020-12066

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-20

Published: April 22, 2020

Last Updated: November 21, 2024

🔗 References

http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00044.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00045.html Mailing List,Third Party Advisory
https://github.com/teeworlds/teeworlds/commit/c68402fa7e279d42886d5951d1ea8ac2facc1ea5 Patch,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AVYG7CCPS5F3OPOQMJKVNXTQ7BXSEX2V/
https://usn.ubuntu.com/4553-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4763 Third Party Advisory
https://www.teeworlds.com/forum/viewtopic.php?id=14785 Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00044.html Mailing List,Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00045.html Mailing List,Third Party Advisory
https://github.com/teeworlds/teeworlds/commit/c68402fa7e279d42886d5951d1ea8ac2facc1ea5 Patch,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AVYG7CCPS5F3OPOQMJKVNXTQ7BXSEX2V/
https://usn.ubuntu.com/4553-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4763 Third Party Advisory
https://www.teeworlds.com/forum/viewtopic.php?id=14785 Vendor Advisory

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