Skipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS
cve-program · CVE-2026-54247
PublishedSkipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
Read the publisher's advisoryeuvd · EUVD-2026-78062
PublishedSkipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
Read the publisher's advisorynvd · CVE-2026-54247
PublishedSkipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
Read the publisher's advisoryosv · GHSA-cwxq-rc9x-2jvv
Published## 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 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 attacker-controlled input - **Preconditions**: Admission webhook endpoint must be network-reachable (default Kubernetes deployment exposes it within cluster network) - **Comparison**: OPA filter has `DefaultMaxRequestBodySize` (1MB) and semaphore-based memory limit; admission handler has neither ## Evidence | File | Lines | Description | |------|-------|-------------| | `dataclients/kubernetes/admission/admission.go` | 76 | `io.ReadAll(r.Body)` without size limit | | `filters/openpolicyagent/openpolicyagent.go` | 68-70 | OPA filter has `DefaultMaxRequestBodySize` = 1MB | | `filters/openpolicyagent/openpolicyagent.go` | 1333-1336 | OPA uses `bufferedBodyReader` with size limits | ## Tests - `dataclients/kubernetes/admission/admission_test.go` exists but **does not test body size limits** ## Impact 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. ## Mitigation 1. Add `http.MaxBytesReader` or equivalent body size limit before `io.ReadAll` 2. Follow the OPA filter pattern: define `DefaultMaxRequestBodySize` and use a buffered reader with size limits 3. Add a configurable `--admission-max-body-size` flag
Read the publisher's advisoryosv · GO-2026-6015
PublishedSkipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS in github.com/zalando/skipper
Read the publisher's advisoryAffected versions, risk and source history
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cve-program · CVE-2026-54247
PublishedSkipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS
Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
- Source published
- 14 Sep 2026 20:04:06 UTC
- Source modified
- 16 Sep 2026 16:19:12 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
euvd · EUVD-2026-78062
PublishedSkipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to …
Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
Additional publisher context
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
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datePublished: Sep 14, 2026, 8:04:06 PM
dateUpdated: Sep 16, 2026, 4:19:12 PM
- Source published
- Sep 14, 2026, 8:04:06 PM (timezone not stated)
- Source modified
- Sep 16, 2026, 4:19:12 PM (timezone not stated)
- Saved here
- 11 Nov 2026 13:59:12 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 3.1 · 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
nvd · CVE-2026-54247
PublishedSkipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to …
Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.22, Handler in dataclients/kubernetes/admission/admission.go passes the body of requests to the Kubernetes admission endpoint at :9443/admission directly to io.ReadAll(r.Body) without a size limit. An attacker with in-cluster network access and a valid Kubernetes client certificate can send a very large body that causes unbounded memory allocation and an out-of-memory termination of the Skipper process. The disruption is limited to Ingress and RouteGroup admission rather than pod creation or unrelated admission controllers, and Kubernetes normally restarts the process. This issue is fixed in version 0.26.22.
Additional publisher context
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Deferred
Weakness classifications: CWE-770
Original publisher date fields
published: 2026-09-14T20:16:45.843
lastModified: 2026-09-16T17:17:20.600
- Source published
- 14 Sep 2026 20:16:45 UTC
- Source modified
- 16 Sep 2026 17:17:20 UTC
- Saved here
- 25 Oct 2026 13:17:22 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · [email protected] · Secondary · 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
osv · GHSA-cwxq-rc9x-2jvv
PublishedSkipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS
## 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 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 attacker-controlled input - **Preconditions**: Admission webhook endpoint must be network-reachable (default Kubernetes deployment exposes it within cluster network) - **Comparison**: OPA filter has `DefaultMaxRequestBodySize` (1MB) and semaphore-based memory limit; admission handler has neither ## Evidence | File | Lines | Description | |------|-------|-------------| | `dataclients/kubernetes/admission/admission.go` | 76 | `io.ReadAll(r.Body)` without size limit | | `filters/openpolicyagent/openpolicyagent.go` | 68-70 | OPA filter has `DefaultMaxRequestBodySize` = 1MB | | `filters/openpolicyagent/openpolicyagent.go` | 1333-1336 | OPA uses `bufferedBodyReader` with size limits | ## Tests - `dataclients/kubernetes/admission/admission_test.go` exists but **does not test body size limits** ## Impact 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. ## Mitigation 1. Add `http.MaxBytesReader` or equivalent body size limit before `io.ReadAll` 2. Follow the OPA filter pattern: define `DefaultMaxRequestBodySize` and use a buffered reader with size limits 3. Add a configurable `--admission-max-body-size` flag
- Source published
- 17 Jul 2026 18:14:08 UTC
- Source modified
- 22 Jul 2026 21:11:38 UTC
- Saved here
- 24 Oct 2026 13:19:41 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Publisher rating · MODERATE
osv · GO-2026-6015
PublishedSkipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS in github.com/zalando/skipper
Skipper: Unbounded Request Body Read in Admission Webhook Causes Memory Exhaustion DoS in github.com/zalando/skipper
- Source published
- 22 Jul 2026 20:36:35 UTC
- Source modified
- 22 Jul 2026 21:00:25 UTC
- Saved here
- 24 Oct 2026 13:19:41 UTC
- Source terms
- OSV · upstream source license applies
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.