CVE-2021-26923
📋 TL;DR
CVE-2021-26923 is an information disclosure vulnerability in Argo CD where the /api/version endpoint leaks internal system information without requiring authentication. This affects all Argo CD deployments before version 1.8.4. Attackers can access sensitive internal data that could aid further attacks.
💻 Affected Systems
- Argo CD
📦 What is this software?
Argo Cd by Argoproj
Argo Cd by Argoproj
⚠️ Risk & Real-World Impact
Worst Case
Attackers obtain detailed internal system information that could enable targeted attacks, privilege escalation, or lateral movement within the environment.
Likely Case
Unauthenticated attackers gather internal system details that reveal deployment architecture, versions, and potentially sensitive configuration information.
If Mitigated
With proper network segmentation and authentication controls, impact is limited to information disclosure only.
🎯 Exploit Status
Simple HTTP GET request to /api/version endpoint without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.8.4 and later
Vendor Advisory: https://github.com/argoproj/argo-cd/security/advisories/GHSA-pfgj-mh5m-2p48
Restart Required: Yes
Instructions:
1. Backup your Argo CD configuration. 2. Update to Argo CD version 1.8.4 or later. 3. Restart Argo CD services. 4. Verify the fix by testing the /api/version endpoint.
🔧 Temporary Workarounds
Network Access Control
allRestrict access to Argo CD API endpoints using network firewalls or security groups.
Reverse Proxy Authentication
allPlace Argo CD behind a reverse proxy that requires authentication before reaching the API.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Argo CD from untrusted networks
- Deploy a web application firewall (WAF) to block unauthorized access to /api/version endpoint
🔍 How to Verify
Check if Vulnerable:
Send HTTP GET request to https://[argo-cd-server]/api/version without authentication. If it returns internal system information, the system is vulnerable.Check Version:
argocd version --clientVerify Fix Applied:
After patching, attempt the same request. It should return 401 Unauthorized or be properly protected.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated requests to /api/version endpoint
- Multiple failed authentication attempts followed by /api/version access
Network Indicators:
- Unusual traffic patterns to /api/version from external IPs
- HTTP GET requests to /api/version without authentication headers
SIEM Query:
source="argo-cd" AND (uri_path="/api/version" AND NOT auth_success="true")