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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-54247: 0.30% estimated exploitation activity in the next 30 days; percentile 22.57 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 For comparison, the OPA filter has a body size limit: 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 multi-GB request body 3. io.ReadAll(r.Body) allocates unbounded memory for the entire body 4. Skipper process is OOM-killed by the Kubernetes kubelet Permission Boundary Analysis - Attacker: Any client with network access to the admission webhook port within the Kubernetes cluster - Boundary crossed: Memory safety — unbounded allocation from…

Published by the source

17 Jul 2026, 18:14 UTC

Last modified by the source

17 Jul 2026, 18:14 UTC

Source last checked

26 Oct 2026, 15:25 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cwxq-rc9x-2jvv

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# Patch Next advisory brief: CVE-2026-54247

Advisory: Skipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS
IDs: CVE-2026-54247, GHSA-cwxq-rc9x-2jvv
Record: https://patchnext.com/advisories/cve-2026-54247 (revision 1, source checked 26 Oct 2026, 15:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/zalando/skipper 0.26.22. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/zalando/skipper: affected < 0.26.22; fixed in 0.26.22

## Suggested inspection (read-only)
- Go github.com/zalando/skipper: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/zalando/skipper.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cwxq-rc9x-2jvv (GitHub-reviewed advisory GHSA-cwxq-rc9x-2jvv lists affected ranges: Go github.com/zalando/skipper >=0 <0.26.22)

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