EUVD-2026-338387

fkie_cve-2026-49998

Centrifugo is an open-source scalable real-time messaging server. Prior to 6.8.1, Centrifugo dynamic JWKS endpoint verification could reuse a key for one allowed issuer to verify a JWT for another allowed issuer because the JWKS cache and singleflight lookup were keyed only by JWT header kid, not by the resolved JWKS endpoint, issuer, audience, or trust-domain namespace, affecting client.token.jwks_public_endpoint, client.subscription_token.jwks_public_endpoint, internal/jwks/cache.go, and internal/jwks/manager.go. This issue is fixed in version 6.8.1.

GHSA-g6vg-wj8f-48cj — Centrifugo's dynamic JWKS key cache keyed only by `kid` allows cross-issuer JWT authentication bypass

Affected: Go: github.com/centrifugal/centrifugo/v6, Go: github.com/centrifugal/centrifugo/v5, Go: github.com/centrifugal/centrifugo/v4, Go: github.com/centrifugal/centrifugo/v3, Go: github.com/centrifugal/centrifugo

#### Summary

Centrifugo's dynamic JWKS endpoint feature can verify a JWT for one allowed issuer using a public key cached from another allowed issuer. The JWKS cache and `singleflight` lookup are keyed only by the JWT header `kid`, not by the resolved JWKS endpoint, issuer, audience, or other trust-domain namespace.

In a documented multi-issuer dynamic JWKS configuration, an attacker who can obtain or mint a valid token for issuer/tenant A can authenticate as issuer/tenant B if both JWKS documents use the same `kid` value and tenant A's key is cached first. This affects connection token verification and subscription token verification because both paths use the same JWKS verification manager.

#### Details

The vulnerable path is reachable when either of these shipped configuration options is set to a templated JWKS URL using values derived from JWT `iss` or `aud` claims:

- `client.token.jwks_public_endpoint` - `client.subscription_token.jwks_public_endpoint`

Relevant shipped config fields are defined in `internal/configtypes/types.go:59-65`, mapped into verifier configuration in `internal/confighelpers/jwt.go:36-41`, and exposed in the generated config schema at `internal/cli/configdoc/schema.json:3927`, `3947`, `3967`, `3987`, `4069`, `4089`, `4109`, and `4129`. Dynamic JWKS endpoints based on `iss` and `aud` are documented in the project changelog at `CHANGELOG.md:107`.

External clients control JWT connection and subscription tokens:

- Connection tokens reach `Verif…

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EUVD-2026-338387

fkie_cve-2026-49998

GHSA-g6vg-wj8f-48cj — Centrifugo's dynamic JWKS key cache keyed only by `kid` allows cross-issuer JWT authentication bypass