CVE-2020-22218
📋 TL;DR
This vulnerability in libssh2 1.10.0 allows attackers to access out-of-bounds memory through the _libssh2_packet_add function. This could lead to information disclosure, denial of service, or potentially remote code execution. Any system using the vulnerable libssh2 library for SSH connections is affected.
💻 Affected Systems
- libssh2
- Applications using libssh2 library
📦 What is this software?
Libssh2 by Libssh2
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, or lateral movement within the network.
Likely Case
Denial of service through application crashes or information disclosure of adjacent memory contents.
If Mitigated
Limited impact with proper network segmentation, minimal exposure, and monitoring in place.
🎯 Exploit Status
Exploitation requires sending specially crafted SSH packets to trigger the out-of-bounds memory access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: libssh2 1.10.1 and later
Vendor Advisory: https://github.com/libssh2/libssh2/pull/476
Restart Required: Yes
Instructions:
1. Update libssh2 to version 1.10.1 or later. 2. Recompile any applications using libssh2. 3. Restart affected services. 4. Verify the fix with version checking.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict SSH access to trusted networks only
iptables -A INPUT -p tcp --dport 22 -s trusted_network -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP
Application Firewall
allImplement WAF or application-level filtering for SSH traffic
🧯 If You Can't Patch
- Implement strict network access controls to limit SSH exposure
- Monitor for abnormal SSH connection patterns and memory access violations
🔍 How to Verify
Check if Vulnerable:
Check libssh2 version: ldd --version | grep libssh2 or check package managerCheck Version:
ldd --version | grep libssh2 || dpkg -l | grep libssh2 || rpm -qa | grep libssh2Verify Fix Applied:
Verify libssh2 version is 1.10.1 or later and applications have been recompiled📡 Detection & Monitoring
Log Indicators:
- Application crashes related to libssh2
- Memory access violation errors
- Abnormal SSH connection terminations
Network Indicators:
- Unusual SSH packet patterns
- Multiple failed SSH connections from single source
SIEM Query:
source="*ssh*" AND (error OR crash OR violation) AND libssh2🔗 References
- https://github.com/libssh2/libssh2/pull/476
- https://lists.debian.org/debian-lts-announce/2023/09/msg00006.html
- https://security.netapp.com/advisory/ntap-20231006-0002/
- https://github.com/libssh2/libssh2/pull/476
- https://lists.debian.org/debian-lts-announce/2023/09/msg00006.html
- https://security.netapp.com/advisory/ntap-20231006-0002/
