Centrifugo's dynamic JWKS key cache keyed only by kid allows cross-issuer JWT authentication bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-49998: 0.22% estimated exploitation activity in the next 30 days; percentile 12.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.jwkspublicendpoint - client.subscriptiontoken.jwkspublicendpoint Relevant shipped config fields are defined in…

Published by the source

1 Jul 2026, 20:28 UTC

Last modified by the source

1 Jul 2026, 20:28 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-g6vg-wj8f-48cj

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-49998

Advisory: Centrifugo's dynamic JWKS key cache keyed only by `kid` allows cross-issuer JWT authentication bypass
IDs: CVE-2026-49998, GHSA-g6vg-wj8f-48cj
Record: https://patchnext.com/advisories/cve-2026-49998 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/centrifugal/centrifugo/v6 6.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/centrifugal/centrifugo/v5: affected <= 5.4.9
- Go github.com/centrifugal/centrifugo/v4: affected <= 4.1.5
- Go github.com/centrifugal/centrifugo/v3: affected <= 3.2.3
- Go github.com/centrifugal/centrifugo/v6: affected <= 6.8.0; fixed in 6.8.1
- Go github.com/centrifugal/centrifugo: affected <= 2.4.0

## Suggested inspection (read-only)
- Go github.com/centrifugal/centrifugo/v5: check the installed version with your package manager.
- Go github.com/centrifugal/centrifugo/v4: check the installed version with your package manager.
- Go github.com/centrifugal/centrifugo/v3: check the installed version with your package manager.
- Go github.com/centrifugal/centrifugo/v6: check the installed version with your package manager.
- Go github.com/centrifugal/centrifugo: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/centrifugal/centrifugo/v5, github.com/centrifugal/centrifugo/v4, github.com/centrifugal/centrifugo/v3, github.com/centrifugal/centrifugo/v6, github.com/centrifugal/centrifugo.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-g6vg-wj8f-48cj (GitHub-reviewed advisory GHSA-g6vg-wj8f-48cj lists affected ranges: Go github.com/centrifugal/centrifugo/v6 >=0 =0 =0 =0 =0 <=2.4.0)

Commands are suggestions: review each one before running it.