Vulnerability-Lookup

CVE-2026-71485 (GCVE-0-2026-71485)

Vulnerability from cvelistv5 – Published: 2026-08-20 21:01 – Updated: 2026-08-25 15:23

Title

Centrifugo: Client-forgeable headers emulation lets any client spoof headers forwarded to proxy backends

Summary

Centrifugo is an open-source scalable real-time messaging server. Prior to 6.9.0, Centrifugo copies the client-controlled protocol.ConnectRequest.headers map through OnClientConnecting in internal/client/handler.go, ConnectEvent.Headers, and SetEmulatedHeadersToContext. The requestHeaders path in internal/proxy/http.go, the requestMetadata path in internal/proxy/grpc.go, and the Consume path in internal/unigrpc/grpc.go can forward an allowlisted value as a trusted backend header or metadata value. A remote client can spoof a header such as x-trusted-user for connect, refresh, subscribe, publish, RPC, and related proxy calls when the backend relies on that header for authentication or authorization. The unidirectional gRPC transport has no transport-level HTTP header that can override the emulated value. This issue is fixed in version 6.9.0.

Severity

9.1 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-25 15:23 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/centrifugal/centrifugo/securit…	x_refsource_CONFIRM
https://github.com/centrifugal/centrifugo/pull/1182	x_refsource_MISC
https://github.com/centrifugal/centrifugo/commit/…	x_refsource_MISC
https://github.com/centrifugal/centrifugo/release…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
centrifugal	centrifugo	Affected: < 6.9.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-71485

Vulnerability from fkie_nvd - Published: 2026-08-20 21:17 - Updated: 2026-08-25 16:17

Severity

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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/centrifugal/centrifugo/commit/84d38cea1dd2efa24375a148817a974c8727f4b0
	security-advisories@github.com	https://github.com/centrifugal/centrifugo/pull/1182
	security-advisories@github.com	https://github.com/centrifugal/centrifugo/releases/tag/v6.9.0
	security-advisories@github.com	https://github.com/centrifugal/centrifugo/security/advisories/GHSA-9468-v6mj-fppw

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "centrifugo",
          "vendor": "centrifugal",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.9.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
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  "descriptions": [
    {
      "lang": "en",
      "value": "Centrifugo is an open-source scalable real-time messaging server. Prior to 6.9.0, Centrifugo copies the client-controlled protocol.ConnectRequest.headers map through OnClientConnecting in internal/client/handler.go, ConnectEvent.Headers, and SetEmulatedHeadersToContext. The requestHeaders path in internal/proxy/http.go, the requestMetadata path in internal/proxy/grpc.go, and the Consume path in internal/unigrpc/grpc.go can forward an allowlisted value as a trusted backend header or metadata value. A remote client can spoof a header such as x-trusted-user for connect, refresh, subscribe, publish, RPC, and related proxy calls when the backend relies on that header for authentication or authorization. The unidirectional gRPC transport has no transport-level HTTP header that can override the emulated value. This issue is fixed in version 6.9.0."
    }
  ],
  "id": "CVE-2026-71485",
  "lastModified": "2026-08-25T16:17:25.460",
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GHSA-9468-V6MJ-FPPW

Vulnerability from github – Published: 2026-09-02 23:41 – Updated: 2026-09-02 23:41

Summary

Centrifugo: Client-forgeable headers emulation lets any client spoof headers forwarded to proxy backends

Details

Vulnerability Details

File: internal/client/handler.go (OnClientConnecting), internal/proxy/http.go (requestHeaders), internal/proxy/grpc.go (requestMetadata), internal/unigrpc/grpc.go (Consume) Line: handler.go:389,548-552 (e.Headers -> SetEmulatedHeadersToContext), http.go:131-165 (requestHeaders), grpc.go:82-114 (requestMetadata), unigrpc/grpc.go:46 (Headers: req.Headers)

Root Cause

The http_headers / grpc_metadata proxy config options are documented as "List of incoming HTTP header names to forward to the proxy backend" / "List of incoming gRPC metadata keys to forward to the proxy backend" -- implying the value originates from the underlying transport connection (e.g. set by a trusted reverse proxy/API gateway in front of Centrifugo). Operators commonly use this to forward identity/trust headers to their own backend for access-control decisions.

However, the wire protocol used by every Centrifugo transport (protocol.ConnectRequest, field headers) includes a headers map populated entirely from the connecting client's own message (its JSON connect command, or for gRPC, its ConnectRequest protobuf field) -- not from real transport-level HTTP headers. Centrifugo copies this client-supplied map verbatim into ConnectEvent.Headers, then into an "emulated headers" context value used by every proxy type (connect, refresh, subscribe, publish, rpc, sub_refresh, map_publish, map_remove, shared_poll_refresh) for the entire connection lifetime. Any header name in the operator's allowlist is forwarded to the backend with the client's own chosen value, unless a header of the exact same name also happens to be present on the genuine underlying HTTP request. For the unidirectional gRPC transport specifically there is no HTTP request at all, so there is no possible override -- the client-controlled value always wins.

Attack Scenario

Operator configures a connect proxy with http_headers: ["x-trusted-user"] (or any header name their backend uses for caller identity/trust).
Attacker connects directly to Centrifugo and sends a connect command containing "headers": {"x-trusted-user": "<any value>"}.
Centrifugo forwards X-Trusted-User: <attacker value> to the backend exactly as if a trusted intermediary had set it.
The backend, trusting this header per its own design, grants whatever access/identity it associates with that value.

Impact

Full spoofing of any header value the backend trusts for authentication/authorization, for every proxy call type, for the lifetime of the connection -- up to full account/identity impersonation depending on backend logic. No credentials, JWT, or API key required.

Vulnerable Code

// internal/proxy/http.go
func requestHeaders(ctx context.Context, allowedHeaders, allowedMetaKeys []string, staticHeaders map[string]string) http.Header {
    headers := http.Header{}
    for k, v := range staticHeaders { headers.Set(k, v) }
    emulatedHeaders, _ := clientcontext.GetEmulatedHeadersFromContext(ctx) // 100% client-controlled
    for k, v := range emulatedHeaders {
        if slices.Contains(allowedHeaders, strings.ToLower(k)) {
            headers.Set(k, v) // forwarded to backend as a real outgoing HTTP header
        }
    }
    httpHeaders, hasHTTPHeaders := middleware.GetHeadersFromContext(ctx) // real headers, if present
    for k, vv := range httpHeaders {
        if slices.Contains(allowedHeaders, strings.ToLower(k)) {
            headers[k] = vv // only overrides if SAME header name was ALSO on the real request
        }
    }
    ...
}

// internal/unigrpc/grpc.go -- never goes through HTTP middleware, no competing real-header check at all
connectRequest := &protocol.ConnectRequest{
    Token: req.Token, Data: req.Data, Name: req.Name, Version: req.Version,
    Headers: req.Headers, // the gRPC client's own protobuf field
}

Recommended Fix

Document explicitly that http_headers/grpc_metadata values can also be supplied by the connecting client itself via "headers emulation" and are not guaranteed to come from a trusted reverse proxy. Provide a separate allowlist (e.g. trusted_http_headers) populated only from genuine transport-level HTTP headers, never from client-supplied ConnectRequest.headers, for operators who need an unforgeable header. For uniGRPC, consider disabling http_headers forwarding entirely since there is no transport-level header concept to fall back on.

Verification

Dynamically confirmed against the official centrifugo/centrifugo:v6.8.3 Docker image on BOTH the bidirectional WebSocket transport and the unidirectional gRPC transport, using a minimal backend that logs every header it receives: - WS: connecting with {"connect": {"headers": {"x-trusted-user": "admin-impersonation-via-headers-emulation"}}} resulted in the backend receiving X-Trusted-User: admin-impersonation-via-headers-emulation, despite no such header existing on the real WebSocket upgrade HTTP request. - uniGRPC: calling the Consume RPC with ConnectRequest(headers={"x-trusted-user": "admin-impersonation-via-unigrpc"}) (zero real gRPC metadata set) resulted in the backend receiving X-Trusted-User: admin-impersonation-via-unigrpc. - Control tests (no headers field / no metadata) confirmed the header is absent from the backend's request in the baseline case.

Severity

9.1 (Critical)


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

9.1 (Critical)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 6.8.4"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/centrifugal/centrifugo"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-71485"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-02T23:41:37Z",
    "nvd_published_at": "2026-08-20T21:17:08Z",
    "severity": "CRITICAL"
  },
  "details": "## Vulnerability Details\n\n**File**: `internal/client/handler.go` (`OnClientConnecting`), `internal/proxy/http.go` (`requestHeaders`), `internal/proxy/grpc.go` (`requestMetadata`), `internal/unigrpc/grpc.go` (`Consume`)\n**Line**: handler.go:389,548-552 (`e.Headers` -\u003e `SetEmulatedHeadersToContext`), http.go:131-165 (`requestHeaders`), grpc.go:82-114 (`requestMetadata`), unigrpc/grpc.go:46 (`Headers: req.Headers`)\n\n### Root Cause\nThe `http_headers` / `grpc_metadata` proxy config options are documented as \"List of incoming HTTP header names to forward to the proxy backend\" / \"List of incoming gRPC metadata keys to forward to the proxy backend\" -- implying the value originates from the underlying transport connection (e.g. set by a trusted reverse proxy/API gateway in front of Centrifugo). Operators commonly use this to forward identity/trust headers to their own backend for access-control decisions.\n\nHowever, the wire protocol used by every Centrifugo transport (`protocol.ConnectRequest`, field `headers`) includes a `headers` map populated entirely from the connecting client\u0027s own message (its JSON `connect` command, or for gRPC, its `ConnectRequest` protobuf field) -- not from real transport-level HTTP headers. Centrifugo copies this client-supplied map verbatim into `ConnectEvent.Headers`, then into an \"emulated headers\" context value used by every proxy type (connect, refresh, subscribe, publish, rpc, sub_refresh, map_publish, map_remove, shared_poll_refresh) for the entire connection lifetime. Any header name in the operator\u0027s allowlist is forwarded to the backend with the client\u0027s own chosen value, unless a header of the exact same name also happens to be present on the genuine underlying HTTP request. For the unidirectional gRPC transport specifically there is no HTTP request at all, so there is no possible override -- the client-controlled value always wins.\n\n### Attack Scenario\n1. Operator configures a connect proxy with `http_headers: [\"x-trusted-user\"]` (or any header name their backend uses for caller identity/trust).\n2. Attacker connects directly to Centrifugo and sends a connect command containing `\"headers\": {\"x-trusted-user\": \"\u003cany value\u003e\"}`.\n3. Centrifugo forwards `X-Trusted-User: \u003cattacker value\u003e` to the backend exactly as if a trusted intermediary had set it.\n4. The backend, trusting this header per its own design, grants whatever access/identity it associates with that value.\n\n### Impact\nFull spoofing of any header value the backend trusts for authentication/authorization, for every proxy call type, for the lifetime of the connection -- up to full account/identity impersonation depending on backend logic. No credentials, JWT, or API key required.\n\n### Vulnerable Code\n```go\n// internal/proxy/http.go\nfunc requestHeaders(ctx context.Context, allowedHeaders, allowedMetaKeys []string, staticHeaders map[string]string) http.Header {\n    headers := http.Header{}\n    for k, v := range staticHeaders { headers.Set(k, v) }\n    emulatedHeaders, _ := clientcontext.GetEmulatedHeadersFromContext(ctx) // 100% client-controlled\n    for k, v := range emulatedHeaders {\n        if slices.Contains(allowedHeaders, strings.ToLower(k)) {\n            headers.Set(k, v) // forwarded to backend as a real outgoing HTTP header\n        }\n    }\n    httpHeaders, hasHTTPHeaders := middleware.GetHeadersFromContext(ctx) // real headers, if present\n    for k, vv := range httpHeaders {\n        if slices.Contains(allowedHeaders, strings.ToLower(k)) {\n            headers[k] = vv // only overrides if SAME header name was ALSO on the real request\n        }\n    }\n    ...\n}\n```\n```go\n// internal/unigrpc/grpc.go -- never goes through HTTP middleware, no competing real-header check at all\nconnectRequest := \u0026protocol.ConnectRequest{\n    Token: req.Token, Data: req.Data, Name: req.Name, Version: req.Version,\n    Headers: req.Headers, // the gRPC client\u0027s own protobuf field\n}\n```\n\n### Recommended Fix\nDocument explicitly that `http_headers`/`grpc_metadata` values can also be supplied by the connecting client itself via \"headers emulation\" and are not guaranteed to come from a trusted reverse proxy. Provide a separate allowlist (e.g. `trusted_http_headers`) populated only from genuine transport-level HTTP headers, never from client-supplied `ConnectRequest.headers`, for operators who need an unforgeable header. For uniGRPC, consider disabling `http_headers` forwarding entirely since there is no transport-level header concept to fall back on.\n\n### Verification\nDynamically confirmed against the official `centrifugo/centrifugo:v6.8.3` Docker image on BOTH the bidirectional WebSocket transport and the unidirectional gRPC transport, using a minimal backend that logs every header it receives:\n- WS: connecting with `{\"connect\": {\"headers\": {\"x-trusted-user\": \"admin-impersonation-via-headers-emulation\"}}}` resulted in the backend receiving `X-Trusted-User: admin-impersonation-via-headers-emulation`, despite no such header existing on the real WebSocket upgrade HTTP request.\n- uniGRPC: calling the `Consume` RPC with `ConnectRequest(headers={\"x-trusted-user\": \"admin-impersonation-via-unigrpc\"})` (zero real gRPC metadata set) resulted in the backend receiving `X-Trusted-User: admin-impersonation-via-unigrpc`.\n- Control tests (no `headers` field / no metadata) confirmed the header is absent from the backend\u0027s request in the baseline case.",
  "id": "GHSA-9468-v6mj-fppw",
  "modified": "2026-09-02T23:41:37Z",
  "published": "2026-09-02T23:41:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/centrifugal/centrifugo/security/advisories/GHSA-9468-v6mj-fppw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-71485"
    },
    {
      "type": "WEB",
      "url": "https://github.com/centrifugal/centrifugo/pull/1182"
    },
    {
      "type": "WEB",
      "url": "https://github.com/centrifugal/centrifugo/commit/84d38cea1dd2efa24375a148817a974c8727f4b0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/centrifugal/centrifugo"
    },
    {
      "type": "WEB",
      "url": "https://github.com/centrifugal/centrifugo/releases/tag/v6.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Centrifugo: Client-forgeable headers emulation lets any client spoof headers forwarded to proxy backends"
}

Sightings

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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.
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Action not permitted

CVE-2026-71485 (GCVE-0-2026-71485)

FKIE_CVE-2026-71485

GHSA-9468-V6MJ-FPPW

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