CVE-2026-42294: Argo Workflows: Unauthenticated Memory Exhaustion (DoS) in Webhook Interceptor

Severity: Medium Component: Webhook Interceptor (server/auth/webhook) Vulnerability Type: Denial of Service (DoS)

Description The Webhook Interceptor loads the entire request body into memory before authenticating the request or verifying its signature. This occurs on the /api/v1/events/ endpoint, which is publicly accessible (albeit intended for webhooks). An attacker can send a request with an extremely large body (e.g., multiple gigabytes), causing the Argo Server to allocate excessive memory, potentially leading to an Out-Of-Memory (OOM) crash and denial of service.

Vulnerable Code In server/auth/webhook/interceptor.go: go func (i WebhookInterceptor) addWebhookAuthorization(r http.Request, kube kubernetes.Interface) error { // ... basic checks ... // Vulnerability: Reads entire body into memory unconditionally buf, := io.ReadAll(r.Body) defer func() { r.Body = io.NopCloser(bytes.NewBuffer(buf)) }() // ... subsequent logic finds correct service account and secret ... // ... verification happens later ... } The io.ReadAll call happens before the signature verification loop.

Impact - Service Availability: An attacker can crash the Argo Server, disrupting workflow execution and API access for all users.

PoC (Conceptual) 1. Target the webhook endpoint: POST /api/v1/events/some-namespace 2. Send a Content-Length: 1000000000 (1GB) header. 3. Stream 1GB of random data. 4. Monitor server memory usage. It will spike until 1GB is allocated or the process crashes.

Recommendation 1. Limit Body Size: Enforce a strict limit on webhook body size (e.g., 10MB) using http.MaxBytesReader. 2. Streaming Verification: If possible, verify the signature in a streaming fashion or use a temporary file for large payloads (though typically webhooks are small).