9.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-32301

CVE-2026-32301: Centrifugo: SSRF via unverified JWT claims interpolated into dynamic JWKS endpoint URL

Centrifugo is an open-source scalable real-time messaging server. Prior to 6.7.0, Centrifugo is vulnerable to Server-Side Request Forgery (SSRF) when configured with a dynamic JWKS endpoint URL using template variables (e.g. {{tenant}}). An unauthenticated attacker can craft a JWT with a malicious iss or aud claim value that gets interpolated into the JWKS fetch URL before the token signature is verified, causing Centrifugo to make an outbound HTTP request to an attacker-controlled destination. This vulnerability is fixed in 6.7.0.

(GitHub Advisory)

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CVE-2026-32301

CVE-2026-32301:

9.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/centrifugal/centrifugo/v6	go	<= 6.6.2	6.7.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a Server-Side Request Forgery (SSRF) in Centrifugo's JWT validation logic for dynamic JWKS endpoints. The root cause is an incorrect order of operations in the VerifyConnectToken and VerifySubscribeToken functions. These functions would parse an incoming JWT and extract values from its claims (specifically iss and aud) to construct a URL for fetching the JSON Web Key Set (JWKS). This construction happened before the JWT's signature was verified.

An unauthenticated attacker could craft a JWT with a forged iss or aud claim pointing to a server they control. When Centrifugo processed this token, the jwks.Manager.fetchKey function would make an HTTP request to the attacker's URL. This allows the attacker to scan the server's internal network, access cloud metadata services to steal credentials, or serve a malicious JWKS file to bypass authentication entirely.

The patch addresses this by reordering the logic. It ensures that the JWT's signature is verified first. Only after a token is confirmed to be authentic are its claims used for any further processing, such as constructing a JWKS URL. Additionally, the patch introduces validation to restrict the values that can be used in the JWKS URL template, preventing path traversal and limiting the allowed values to a predefined set.

Vulnerable functions

jwtverify.VerifierJWT.VerifyConnectToken

internal/jwtverify/token_verifier_jwt.go

This function is responsible for verifying a client's connection token. The vulnerability lies in the order of operations. Before the patch, it would extract claims (like 'iss' and 'aud') from the JWT and use them to construct a JWKS URL *before* verifying the token's signature. An attacker could provide a malicious 'iss' or 'aud' claim in an unsigned JWT, causing the server to make a request to an attacker-controlled URL when fetching the JWKS key set. This is a Server-Side Request Forgery (SSRF) vulnerability.

jwtverify.VerifierJWT.VerifySubscribeToken

internal/jwtverify/token_verifier_jwt.go

Similar to `VerifyConnectToken`, this function verifies a client's subscription token. It shared the same logical flaw where it used unverified claims from the JWT to dynamically construct a JWKS URL for signature verification, leading to an SSRF vulnerability. An attacker could craft a malicious JWT to force the server to make requests to arbitrary internal or external endpoints.

jwks.Manager.fetchKey

internal/jwks/manager.go

This function is the sink for the SSRF vulnerability. It takes template variables (`tokenVars`), which are derived from unverified JWT claims, and uses them to construct a URL (`jwkURL`). It then proceeds to make an HTTP GET request to this URL. Because the `tokenVars` are attacker-controlled, the `jwkURL` can be manipulated to point to any server or IP address, thus triggering the SSRF.

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Miggo AI

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WAF Rule

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Reasoning

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