Vulnerability-Lookup

CVE-2026-54246 (GCVE-0-2026-54246)

Vulnerability from cvelistv5 – Published: 2026-09-14 20:03 – Updated: 2026-09-15 14:38

Title

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

Summary

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.

Severity

5.7 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-15 14:38 UTC

CWE

CWE-306 - Missing Authentication for Critical Function

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/zalando/skipper/security/advis…	x_refsource_CONFIRM
https://github.com/zalando/skipper/pull/4056	x_refsource_MISC
https://github.com/zalando/skipper/commit/fb3d5f9…	x_refsource_MISC
https://github.com/zalando/skipper/releases/tag/v…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
zalando	skipper	Affected: < 0.27.13	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-54246

Vulnerability from fkie_nvd - Published: 2026-09-14 20:16 - Updated: 2026-09-16 13:42

Severity

5.7 (Medium) - CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/zalando/skipper/commit/fb3d5f98ee749d9a1dfc5df2d51ac9b82fab92aa
	security-advisories@github.com	https://github.com/zalando/skipper/pull/4056
	security-advisories@github.com	https://github.com/zalando/skipper/releases/tag/v0.27.13
	security-advisories@github.com	https://github.com/zalando/skipper/security/advisories/GHSA-5587-2x54-jj6h

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "skipper",
          "vendor": "zalando",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.27.13"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
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    {
      "lang": "en",
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    }
  ],
  "id": "CVE-2026-54246",
  "lastModified": "2026-09-16T13:42:48.877",
  "metrics": {
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      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "ADJACENT_NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.7,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.1,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
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  "references": [
    {
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      "url": "https://github.com/zalando/skipper/commit/fb3d5f98ee749d9a1dfc5df2d51ac9b82fab92aa"
    },
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      "source": "security-advisories@github.com",
      "url": "https://github.com/zalando/skipper/pull/4056"
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    }
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      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-5587-2X54-JJ6H

Vulnerability from github – Published: 2026-07-17 21:46 – Updated: 2026-07-17 21:46

Summary

Skipper's routesrv-no-auth component: All routesrv API Endpoints Lack Authentication

Details

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:

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:

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:

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:

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

Initial Compromise: Attacker compromises any pod in the Kubernetes cluster (via application CVE, supply-chain attack, malicious container image, etc.)
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)
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
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

Add authentication to all routesrv HTTP endpoints (basic auth, bearer token, mTLS, or shared secret) via flag -route-server-filters=""
Deploy Kubernetes NetworkPolicies restricting ingress to routesrv to only the data-plane skipper pod selectors
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

Severity

5.7 (Medium)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/zalando/skipper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.27.13"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54246"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-17T21:46:18Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Description\n\nThe `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.\n\n## Vulnerable Code\n\n**routesrv/routesrv.go:87-99,114-137** \u2014 all handler registrations on the main mux:\n```go\nmux.Handle(\"/routes\", b)          // eskipBytes.ServeHTTP \u2014 all route data\nmux.Handle(\"/routes/{zone}\", b)   // zone-scoped route data\nmux.Handle(\"/swarm/redis/shards\", rh)   // Redis cluster addresses\nmux.Handle(\"/swarm/valkey/shards\", vh)  // Valkey cluster addresses\n```\n\n**routesrv/eskipbytes.go:134-196** \u2014 `eskipBytes.ServeHTTP`:\n```go\nfunc (e *eskipBytes) ServeHTTP(rw http.ResponseWriter, r *http.Request) {\n    // ... only checks GET/HEAD method, NO auth check\n    if r.Method != \"GET\" \u0026\u0026 r.Method != \"HEAD\" {\n        w.WriteHeader(http.StatusMethodNotAllowed)\n        return\n    }\n    // ... serves all route data immediately\n}\n```\n\n**routesrv/redishandler.go:28-41** \u2014 `RedisHandler.ServeHTTP`:\n```go\nfunc (rh *RedisHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {\n    if r.Method != \"GET\" {\n        w.WriteHeader(http.StatusMethodNotAllowed)\n        return\n    }\n    // ... serves Redis cluster addresses immediately, NO auth check\n}\n```\n\n**routesrv/valkeyhandler.go:28-41** \u2014 `ValkeyHandler.ServeHTTP`:\n```go\nfunc (vh *ValkeyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {\n    if r.Method != \"GET\" {\n        w.WriteHeader(http.StatusMethodNotAllowed)\n        return\n    }\n    // ... serves Valkey cluster addresses immediately, NO auth check\n}\n```\n\n## Attack Path\n\n1. **Initial Compromise**: Attacker compromises any pod in the Kubernetes cluster (via application CVE, supply-chain attack, malicious container image, etc.)\n2. **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`)\n3. **Data Extraction without Auth**: \n   - `GET http://\u003croutesrv\u003e:9090/routes` \u2192 All Ingress/RouteGroup configurations across ALL namespaces\n   - `GET http://\u003croutesrv\u003e:9090/swarm/redis/shards` \u2192 Redis cache cluster node addresses\n   - `GET http://\u003croutesrv\u003e:9090/swarm/valkey/shards` \u2192 Valkey cache cluster node addresses\n4. **Subsequent Attacks**: With cache cluster topology, attacker can perform direct cache-level attacks (ratelimit data manipulation, session data exfiltration)\n\n## Permission Boundary Analysis\n\nThe 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**.\n\nA 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\"*.\n\nNo 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.\n\n## Exposed Data\n\n| Endpoint | Data Exposed | Impact |\n|----------|-------------|--------|\n| `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 |\n| `GET /routes/{zone}` | Zone-scoped subset of above route data | Same, scoped |\n| `GET /swarm/redis/shards` | Redis cluster internal IP:port pairs | Direct cache-level attacks, ratelimit data manipulation |\n| `GET /swarm/valkey/shards` | Valkey cluster internal IP:port pairs | Same |\n\nAdditionally, the data-plane client (`eskipfile/remote.go:190-219`) also performs plain HTTP GET with no credentials \u2014 only an ETag header is sent \u2014 confirming that no auth capability exists in the architecture at all.\n\n\n## Mitigation\n\n1. Add authentication to all routesrv HTTP endpoints (basic auth, bearer token, mTLS, or shared secret) via flag `-route-server-filters=\"\"`\n2. Deploy Kubernetes NetworkPolicies restricting ingress to routesrv to only the data-plane skipper pod selectors\n3. Consider using mutual TLS authentication between data-plane and control-plane components\n\n\n### NetworkPolicy does not remove the missing-auth condition\nRestrictive 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.\n\n### Impact framing\nThis 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.\n\n## Resources\n\n- `routesrv/routesrv.go:87-99` \u2014 handler registration (zero auth)\n- `routesrv/eskipbytes.go:134-196` \u2014 route data handler (no auth)\n- `routesrv/redishandler.go:28-41` \u2014 Redis shard handler (no auth)\n- `routesrv/valkeyhandler.go:28-41` \u2014 Valkey shard handler (no auth)\n- `dataclients/kubernetes/clusterclient.go:648-653` \u2014 `fetchClusterState()` \u2014 shows cluster-wide RBAC\n- `eskipfile/remote.go:190-219` \u2014 data-plane client also has no auth capability\n- `docs/tutorials/operations.md:108`, `docs/tutorials/ratelimit.md:137,197` \u2014 documented routesrv DNS name",
  "id": "GHSA-5587-2x54-jj6h",
  "modified": "2026-07-17T21:46:18Z",
  "published": "2026-07-17T21:46:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/zalando/skipper/security/advisories/GHSA-5587-2x54-jj6h"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/zalando/skipper"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zalando/skipper/releases/tag/v0.27.13"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Skipper\u0027s routesrv-no-auth component: All routesrv API Endpoints Lack Authentication"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-54246 (GCVE-0-2026-54246)

FKIE_CVE-2026-54246

GHSA-5587-2X54-JJ6H

Description

Vulnerable Code

Attack Path

Permission Boundary Analysis

Exposed Data

Mitigation

NetworkPolicy does not remove the missing-auth condition

Impact framing

Resources

Tags

Sightings

Nomenclature

Related by attack behaviour