CVE-2021-34182
📋 TL;DR
CVE-2021-34182 is a critical vulnerability in ttyd v1.6.3 that allows attackers to execute arbitrary code due to insecure default configuration permissions. This affects systems running ttyd with default settings, potentially giving attackers full control over affected systems. The vulnerability is particularly dangerous because it requires minimal attacker interaction.
💻 Affected Systems
- ttyd
📦 What is this software?
Ttyd by Ttyd Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, allowing attackers to install malware, exfiltrate data, pivot to other systems, or establish persistent backdoors.
Likely Case
Remote code execution leading to unauthorized system access, data theft, and potential lateral movement within the network.
If Mitigated
Limited impact with proper network segmentation and access controls, potentially preventing exploitation or containing damage.
🎯 Exploit Status
Exploitation is straightforward due to default insecure permissions; public discussions and proof-of-concepts exist in GitHub issues.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 1.6.4 and later
Vendor Advisory: https://github.com/tsl0922/ttyd/issues/692
Restart Required: Yes
Instructions:
1. Stop ttyd service. 2. Update to ttyd v1.6.4 or later using package manager or source compilation. 3. Restart ttyd service. 4. Verify new version is running.
🔧 Temporary Workarounds
Change default permissions
linuxModify ttyd configuration to use secure permissions instead of default insecure settings
ttyd --credential username:password --port 8080 --client-option disableResizeOverlay=true
Network isolation
linuxRestrict network access to ttyd service using firewall rules
iptables -A INPUT -p tcp --dport 8080 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP
🧯 If You Can't Patch
- Immediately disable ttyd service on all affected systems
- Implement strict network access controls to limit exposure to trusted IPs only
🔍 How to Verify
Check if Vulnerable:
Check ttyd version: 'ttyd --version' should show 1.6.3. Also check if running with default insecure configuration.Check Version:
ttyd --versionVerify Fix Applied:
Verify version is 1.6.4 or later: 'ttyd --version'. Check configuration uses secure settings like authentication.📡 Detection & Monitoring
Log Indicators:
- Unauthorized connection attempts to ttyd port
- Unusual process execution from ttyd sessions
- Failed authentication attempts if authentication enabled
Network Indicators:
- Unexpected connections to ttyd default port (typically 8080)
- Suspicious network traffic patterns from ttyd instances
SIEM Query:
source="ttyd.log" AND (event="unauthorized_access" OR event="execution_failure")