vulnerability / NVI-00016023 / Revision 1
Skipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS
GitHub lists this reviewed advisory for github.com/zalando/skipper. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
4.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
github.com/zalando/skipper
source listed< 0.26.22
## Summary The Kubernetes admission webhook handler reads the entire request body using `io.ReadAll(r.Body)` without any size limit. Any client that can reach the webhook port within the cluster can send a multi-GB payload, causing the skipper process to exhaust memory and be OOM-killed. This disrupts all Kubernetes admission control, potentially blocking all pod creation and updates. ## Vulnerable Code ```go // 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) ``` For comparison, the OPA filter has a body size limit: ```go // filters/openpolicyagent/openpolicyagent.go:68-70 const DefaultMaxRequestBodySize = 1 << 20 // 1MB // OPA uses a bufferedBodyReader with size limits ``` ## Attack Path 1. Attacker identifies the admission webhook endpoint (default: `:9443/admission` or configured path) 2. Attacker sends: `POST /admission HTTP/1.1, Content-Type: application/json` with a mul
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-cwxq-rc9x-2jvv ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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