CVE-2024-21661 – CVE-2024-21661 is a critical Denial of Service ... (How to Fix)

Q: What is the severity of CVE-2024-21661?

CVE-2024-21661 has a CVSS score of 7.5 (HIGH). CVE-2024-21661 is a critical Denial of Service vulnerability in Argo CD that allows unauthenticated attackers to crash the application by exploiting unsafe array manipulation in multi-threaded environments. All Argo CD users running vulnerable versions are affected, as the flaw can render the application completely inoperable. The vulnerability stems from concurrent modification of an array while it's being iterated over, causing application crashes.

📋 TL;DR

CVE-2024-21661 is a critical Denial of Service vulnerability in Argo CD that allows unauthenticated attackers to crash the application by exploiting unsafe array manipulation in multi-threaded environments. All Argo CD users running vulnerable versions are affected, as the flaw can render the application completely inoperable. The vulnerability stems from concurrent modification of an array while it's being iterated over, causing application crashes.

💻 Affected Systems

Products:

Argo CD

Versions: All versions prior to 2.8.13, 2.9.9, and 2.10.4

Operating Systems: All platforms running Argo CD

Default Config Vulnerable: ⚠️ Yes

Notes: All Argo CD deployments with default configurations are vulnerable. No special configuration required for exploitation.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete and persistent denial of service where Argo CD becomes completely unavailable, disrupting all GitOps deployments and Kubernetes management operations.

🟠

Likely Case

Intermittent application crashes leading to service disruption, failed deployments, and operational downtime until the application is restarted.

🟢

If Mitigated

Limited impact if network controls restrict access to Argo CD API endpoints and proper monitoring detects crash patterns early.

🌐 Internet-Facing: HIGH

🏢 Internal Only: HIGH

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

The vulnerability requires no authentication and exploits a simple race condition, making exploitation straightforward for attackers with network access to Argo CD.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.8.13, 2.9.9, or 2.10.4

Vendor Advisory: https://github.com/argoproj/argo-cd/security/advisories/GHSA-6v85-wr92-q4p7

Restart Required: Yes

Instructions:

1. Identify current Argo CD version. 2. Upgrade to patched version (2.8.13 for 2.8.x, 2.9.9 for 2.9.x, 2.10.4 for 2.10.x). 3. Restart Argo CD components. 4. Verify the upgrade was successful.

🔧 Temporary Workarounds

Network Access Restriction

all

Restrict network access to Argo CD API endpoints to trusted IP addresses only

# Example using Kubernetes NetworkPolicy
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: argo-cd-restrict
  namespace: argocd
spec:
  podSelector:
    matchLabels:
      app.kubernetes.io/name: argocd-server
  policyTypes:
  - Ingress
  ingress:
  - from:
    - ipBlock:
        cidr: 10.0.0.0/8  # Restrict to internal network

🧯 If You Can't Patch

Implement strict network segmentation to limit access to Argo CD API endpoints
Deploy rate limiting and request filtering at the ingress/load balancer level

🔍 How to Verify

Check if Vulnerable:

Check Argo CD version: kubectl get pods -n argocd -l app.kubernetes.io/name=argocd-server -o jsonpath='{.items[0].spec.containers[0].image}'

Check Version:

kubectl get pods -n argocd -l app.kubernetes.io/name=argocd-server -o jsonpath='{.items[0].spec.containers[0].image}'

Verify Fix Applied:

Verify version is 2.8.13, 2.9.9, or 2.10.4 or higher: kubectl get pods -n argocd -l app.kubernetes.io/name=argocd-server -o jsonpath='{.items[0].spec.containers[0].image}' | grep -E '2\.8\.13|2\.9\.9|2\.10\.4'

📡 Detection & Monitoring

Log Indicators:

Argo CD process crashes
Panic stack traces in logs
Repeated pod restarts in Kubernetes
Error messages related to concurrent map/slice access

Network Indicators:

High volume of requests to Argo CD API endpoints from single sources
Unusual request patterns targeting session management endpoints

SIEM Query:

source="argo-cd" AND ("panic" OR "fatal" OR "concurrent map" OR "concurrent slice" OR "crash")

📊 Metadata

CVE ID: CVE-2024-21661

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-787

Published: March 18, 2024

Last Updated: January 9, 2025

🔗 References

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🔗 Related Vulnerabilities

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📋 TL;DR

💻 Affected Systems

📦 What is this software?

Argo Cd by Argoproj

Argo Cd by Argoproj

Argo Cd by Argoproj

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Network Access Restriction

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export

🔗 Related Vulnerabilities