Authentication bypass via untrusted JWT algorithm selection
Published Jan 13, 2026 · Updated Jan 13, 2026
Algorithm confusion in Hono before 4.11.4 allows remote attackers to forge JWTs and bypass authentication in affected applications. The JWK/JWKS JWT verification path falls back from a JWK lacking alg to the unverified token header's alg, allowing attacker-controlled algorithm selection. Exploitation requires an application that uses the JWK/JWKS middleware for authorization without an explicit algorithm restriction; other Hono deployments are unaffected.
Summary
What happened
Algorithm confusion in Hono before 4.11.4 allows remote attackers to forge JWTs and bypass authentication in affected applications. The JWK/JWKS JWT verification path falls back from a JWK lacking alg to the unverified token header's alg, allowing attacker-controlled algorithm selection. Exploitation requires an application that uses the JWK/JWKS middleware for authorization without an explicit algorithm restriction; other Hono deployments are unaffected.
The record
- CVE
- CVE-2026-22817
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Hono
- Product
- Hono
- Classifications
- CWE-347, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 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=< 4.11.4
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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