Skipper routesrv-no-auth: All routesrv API Endpoints Lack Authentication

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Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.27.13, the routesrv component serves cluster-wide control-plane data without application-layer authentication through /routes, /routes/{zone}, /swarm/redis/shards, and /swarm/valkey/shards. The handlers registered in routesrv/routesrv.go, eskipBytes.ServeHTTP in routesrv/eskipbytes.go, RedisHandler.ServeHTTP in routesrv/redishandler.go, and ValkeyHandler.ServeHTTP in routesrv/valkeyhandler.go only restrict HTTP methods and do not authenticate callers. A compromised or otherwise attacker-controlled pod that can reach routesrv on the Kubernetes cluster network can bypass its namespace-scoped RBAC and read Ingress and RouteGroup backend URLs, filter-chain and OAuth or OIDC path details, and Redis or Valkey shard addresses across namespaces. NetworkPolicy can restrict reachability but does not remove the missing-authentication condition, and the established impact is confidentiality exposure rather than direct integrity or availability loss. This issue is fixed in version 0.27.13.

Source published

14 Sep 2026 20:03:14 UTC

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15 Sep 2026 14:38:38 UTC

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23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.27.13, the routesrv component serves cluster-wide control-plane data without application-layer authentication through /routes, /routes/{zone}, /swarm/redis/shards, and /swarm/valkey/shards. The handlers registered in routesrv/routesrv.go, eskipBytes.ServeHTTP in routesrv/eskipbytes.go, RedisHandler.ServeHTTP in routesrv/redishandler.go, and ValkeyHandler.ServeHTTP in routesrv/valkeyhandler.go only restrict HTTP methods and do not authenticate callers. A compromised or otherwise attacker-controlled pod that can reach routesrv on the Kubernetes cluster network can bypass its namespace-scoped RBAC and read Ingress and RouteGroup backend URLs, filter-chain and OAuth or OIDC path details, and Redis or Valkey shard addresses across namespaces. NetworkPolicy can restrict reachability but does not remove the missing-authentication condition, and the established impact is confidentiality exposure rather than direct integrity or availability loss. This issue is fixed in version 0.27.13.

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Sep 14, 2026, 8:03:14 PM (timezone not stated)

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Sep 15, 2026, 2:38:38 PM (timezone not stated)

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11 Nov 2026 13:59:10 UTC

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EUVD CVSS 3.1 · 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.27.13, the routesrv component serves cluster-wide control-plane data without application-layer authentication through /routes, /routes/{zone}, /swarm/redis/shards, and /swarm/valkey/shards. The handlers registered in routesrv/routesrv.go, eskipBytes.ServeHTTP in routesrv/eskipbytes.go, RedisHandler.ServeHTTP in routesrv/redishandler.go, and ValkeyHandler.ServeHTTP in routesrv/valkeyhandler.go only restrict HTTP methods and do not authenticate callers. A compromised or otherwise attacker-controlled pod that can reach routesrv on the Kubernetes cluster network can bypass its namespace-scoped RBAC and read Ingress and RouteGroup backend URLs, filter-chain and OAuth or OIDC path details, and Redis or Valkey shard addresses across namespaces. NetworkPolicy can restrict reachability but does not remove the missing-authentication condition, and the established impact is confidentiality exposure rather than direct integrity or availability loss. This issue is fixed in version 0.27.13.

Source published

14 Sep 2026 20:16:45 UTC

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16 Sep 2026 13:42:48 UTC

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25 Oct 2026 13:17:22 UTC

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CVSS 3.1 · [email protected] · Secondary · 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

## Description The `routesrv` component exposes the full cluster route topology (Ingress/RouteGroup configurations, backend URLs, filter chains, OAuth/OIDC callback paths) and cache-cluster topology (Redis/Valkey shard addresses) over plain HTTP with **zero authentication**. Any pod in the Kubernetes cluster can reach routesrv via its predictable DNS name and retrieve sensitive cluster-wide routing and cache infrastructure data. ## Vulnerable Code **routesrv/routesrv.go:87-99,114-137** — all handler registrations on the main mux: ```go mux.Handle("/routes", b) // eskipBytes.ServeHTTP — all route data mux.Handle("/routes/{zone}", b) // zone-scoped route data mux.Handle("/swarm/redis/shards", rh) // Redis cluster addresses mux.Handle("/swarm/valkey/shards", vh) // Valkey cluster addresses ``` **routesrv/eskipbytes.go:134-196** — `eskipBytes.ServeHTTP`: ```go func (e *eskipBytes) ServeHTTP(rw http.ResponseWriter, r *http.Request) { // ... only checks GET/HEAD method, NO auth check if r.Method != "GET" && r.Method != "HEAD" { w.WriteHeader(http.StatusMethodNotAllowed) return } // ... serves all route data immediately } ``` **routesrv/redishandler.go:28-41** — `RedisHandler.ServeHTTP`: ```go func (rh *RedisHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { if r.Method != "GET" { w.WriteHeader(http.StatusMethodNotAllowed) return } // ... serves Redis cluster addresses immediately, NO auth check } ``` **routesrv/valkeyhandler.go:28-41** — `ValkeyHandler.ServeHTTP`: ```go func (vh *ValkeyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { if r.Method != "GET" { w.WriteHeader(http.StatusMethodNotAllowed) return } // ... serves Valkey cluster addresses immediately, NO auth check } ``` ## Attack Path 1. **Initial Compromise**: Attacker compromises any pod in the Kubernetes cluster (via application CVE, supply-chain attack, malicious container image, etc.) 2. **Discovery**: Attacker discovers routesrv via predictable Kubernetes DNS name: `skipper-ingress-routesrv.kube-system.svc.cluster.local:9090` (documented at `docs/tutorials/operations.md:108`, `docs/tutorials/ratelimit.md:137,197`) 3. **Data Extraction without Auth**: - `GET http://<routesrv>:9090/routes` → All Ingress/RouteGroup configurations across ALL namespaces - `GET http://<routesrv>:9090/swarm/redis/shards` → Redis cache cluster node addresses - `GET http://<routesrv>:9090/swarm/valkey/shards` → Valkey cache cluster node addresses 4. **Subsequent Attacks**: With cache cluster topology, attacker can perform direct cache-level attacks (ratelimit data manipulation, session data exfiltration) ## Permission Boundary Analysis The routesrv uses a ServiceAccount with **cluster-wide RBAC** to list Ingress (networking.k8s.io), RouteGroup (zalando.org), Endpoints, and Services across all namespaces (see `clusterclient.go:648-653` `fetchClusterState`). The kube-apiserver requires proper ServiceAccount token + RBAC authorization for the Kubernetes API itself, but **routesrv exposes the aggregated data over HTTP with zero authentication**. A compromised pod with limited RBAC (restricted to its own namespace) can bypass Kubernetes RBAC entirely by reading routesrv. This crosses the boundary from *"namespace-scoped Kubernetes workload with restricted RBAC"* to *"full cluster route topology across all namespaces"*. No NetworkPolicy manifests exist in the `deploy/` directory. The default Kubernetes flat network model allows any pod to reach any service, further widening the attack surface. ## Exposed Data | Endpoint | Data Exposed | Impact | |----------|-------------|--------| | `GET /routes` | All ingress/routegroup backends: internal service URLs, filter chains (auth, rate limiting, OAuth, JWT, OPA policies), load balancer group membership | Cluster-wide reconnaissance, targeted backend attacks | | `GET /routes/{zone}` | Zone-scoped subset of above route data | Same, scoped | | `GET /swarm/redis/shards` | Redis cluster internal IP:port pairs | Direct cache-level attacks, ratelimit data manipulation | | `GET /swarm/valkey/shards` | Valkey cluster internal IP:port pairs | Same | Additionally, the data-plane client (`eskipfile/remote.go:190-219`) also performs plain HTTP GET with no credentials — only an ETag header is sent — confirming that no auth capability exists in the architecture at all. ## Mitigation 1. Add authentication to all routesrv HTTP endpoints (basic auth, bearer token, mTLS, or shared secret) via flag `-route-server-filters=""` 2. Deploy Kubernetes NetworkPolicies restricting ingress to routesrv to only the data-plane skipper pod selectors 3. Consider using mutual TLS authentication between data-plane and control-plane components ### NetworkPolicy does not remove the missing-auth condition Restrictive NetworkPolicies are a valid mitigation, but they are not an application-layer authentication mechanism. The security-relevant defect remains that routesrv serves control-plane-derived data to unauthenticated callers whenever network reachability exists. ### Impact framing This report does **not** rely on claiming direct integrity or availability impact. The verified issue is a confidentiality-focused control-plane exposure: route definitions, backend topology, filter-chain details, and Redis/Valkey shard addresses become readable to any reachable in-cluster client. ## Resources - `routesrv/routesrv.go:87-99` — handler registration (zero auth) - `routesrv/eskipbytes.go:134-196` — route data handler (no auth) - `routesrv/redishandler.go:28-41` — Redis shard handler (no auth) - `routesrv/valkeyhandler.go:28-41` — Valkey shard handler (no auth) - `dataclients/kubernetes/clusterclient.go:648-653` — `fetchClusterState()` — shows cluster-wide RBAC - `eskipfile/remote.go:190-219` — data-plane client also has no auth capability - `docs/tutorials/operations.md:108`, `docs/tutorials/ratelimit.md:137,197` — documented routesrv DNS name

Source published

17 Jul 2026 21:46:18 UTC

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22 Jul 2026 21:11:26 UTC

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24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

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Skipper's routesrv-no-auth component: All routesrv API Endpoints Lack Authentication in github.com/zalando/skipper

Source published

22 Jul 2026 20:36:35 UTC

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22 Jul 2026 21:00:24 UTC

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