fkie_cve-2026-71485

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.

GHSA-9468-v6mj-fppw — Centrifugo: Client-forgeable headers emulation lets any client spoof headers forwarded to proxy backends

Affected: Go: github.com/centrifugal/centrifugo

## 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…

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fkie_cve-2026-71485

GHSA-9468-v6mj-fppw — Centrifugo: Client-forgeable headers emulation lets any client spoof headers forwarded to proxy backends