CVE-2026-42294

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:

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.

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.

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

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

Kodem intelligence

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).

1. What is CVE-2026-42294? CVE-2026-42294 is a high-severity allocation of resources without limits or throttling vulnerability in github.com/argoproj/argo-workflows/v3 (go), affecting versions < 3.7.14. It is fixed in 3.7.14, 4.0.5. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. Which packages are affected by CVE-2026-42294?
   • github.com/argoproj/argo-workflows/v3 (go) (versions < 3.7.14)
   • github.com/argoproj/argo-workflows/v4 (go) (versions >= 4.0.0, < 4.0.5)
3. Is there a fix for CVE-2026-42294? Yes. CVE-2026-42294 is fixed in 3.7.14, 4.0.5. Upgrade to this version or later.
4. Is CVE-2026-42294 exploitable, and should I be worried? Whether CVE-2026-42294 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
5. What actually determines whether CVE-2026-42294 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.
6. How do I fix CVE-2026-42294?
   • Upgrade github.com/argoproj/argo-workflows/v3 to 3.7.14 or later
   • Upgrade github.com/argoproj/argo-workflows/v4 to 4.0.5 or later