Authentication bypass via unverified JWT claim interpolation
Published Mar 12, 2026 · Updated Mar 12, 2026
SSRF in Centrifugo before 6.7.0 allows remote attackers to redirect JWKS fetches and forge authentication via crafted JWT claims. VerifyConnectToken and VerifySubscribeToken extract regex captures from unverified iss or aud claims, and fetchKey interpolates them into the JWKS URL before signature verification. Exploitation requires a dynamic JWKS endpoint template plus issuer_regex or audience_regex captures that accept attacker-chosen values; successful key substitution accepts attacker-signed tokens.
Summary
What happened
SSRF in Centrifugo before 6.7.0 allows remote attackers to redirect JWKS fetches and forge authentication via crafted JWT claims. VerifyConnectToken and VerifySubscribeToken extract regex captures from unverified iss or aud claims, and fetchKey interpolates them into the JWKS URL before signature verification. Exploitation requires a dynamic JWKS endpoint template plus issuer_regex or audience_regex captures that accept attacker-chosen values; successful key substitution accepts attacker-signed tokens.
The record
- CVE
- CVE-2026-32301
- Published
- Mar 12, 2026
- Updated
- Mar 12, 2026
- Vendor
- Centrifugal Labs
- Product
- Centrifugo
- Classifications
- CWE-918, CAPEC-664, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 12, 2026CVE publishedPublication date reported by the CVE source.
- Mar 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 6.7.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-j77h-rr39-c552 WebSocket callback proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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