CVE-2026-54247

Skipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS

// dataclients/kubernetes/admission/admission.go:76
body, err := io.ReadAll(r.Body)  // <-- NO SIZE LIMIT
if err != nil {
    log.Errorf("Failed to read request: %v", err)
    w.WriteHeader(http.StatusInternalServerError)
    invalidRequests.WithLabelValues(admitterName).Inc()
    return
}

var review admissionReview
err = json.Unmarshal(body, &review)

// filters/openpolicyagent/openpolicyagent.go:68-70
const DefaultMaxRequestBodySize = 1 << 20 // 1MB

// OPA uses a bufferedBodyReader with size limits

The admission webhook handler reads the entire request body using io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a multi-GB payload to the webhook endpoint, causing the skipper process to exhaust memory and be OOM-killed. This disrupts admission control for Ingress and RouteGroup resources until the process is automatically restarted by the kubelet.

Scope of impact: Ingress and RouteGroup admission only, not pod creation or other admission controllers.

Recovery: Kubernetes automatically restarts the OOM-killed process, limiting downtime.

Prerequisites: (1) In-cluster network access to the webhook port, (2) valid Kubernetes client certificate.

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.

CVE-2026-54247 has a CVSS score of 4.3 (Medium). The vector is network-reachable, low 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 (0.26.22); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2026-54247? CVE-2026-54247 is a medium-severity allocation of resources without limits or throttling vulnerability in github.com/zalando/skipper (go), affecting versions < 0.26.22. It is fixed in 0.26.22. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-54247? CVE-2026-54247 has a CVSS score of 4.3 (Medium). 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 versions of github.com/zalando/skipper are affected by CVE-2026-54247? github.com/zalando/skipper (go) versions < 0.26.22 is affected.
4. Is there a fix for CVE-2026-54247? Yes. CVE-2026-54247 is fixed in 0.26.22. Upgrade to this version or later.
5. Is CVE-2026-54247 exploitable, and should I be worried? Whether CVE-2026-54247 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-2026-54247 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-2026-54247? Upgrade github.com/zalando/skipper to 0.26.22 or later.

Other vulnerabilities in github.com/zalando/skipper