CVE-2026-22817 JWT Algorithm Confusion via Unsafe Default (HS256) in Hono JWT Middleware Allows Token Forgery and Auth Bypass

What is CVE-2026-22817?

CVE-2026-22817 is a high-severity vulnerability in honojs hono, published on 13 Jan 2026.

Official description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.11.4, there is a flaw in Hono’s JWK/JWKS JWT verification middleware allowed the JWT header’s alg value to influence signature verification when the selected JWK did not explicitly specify an algorithm. This could enable JWT algorithm confusion and, in certain configurations, allow forged tokens to be accepted. As part of this fix, the JWT middleware now requires the alg option to be explicitly specified. This prevents algorithm confusion by ensuring that the verification algorithm is not derived from untrusted JWT header values. This vulnerability is fixed in 4.11.4.

Weakness: CWE-347

Which versions are affected by CVE-2026-22817?

2 open source packages ship an affected version, including hono. It affects 1 product.

Products include Hono Hono.

How do I fix CVE-2026-22817?

Upgrade hono to 4.11.4 or later.

Is CVE-2026-22817 being exploited?

There is no known exploitation of CVE-2026-22817 in the wild and no public exploit code.

Other vulnerabilities in honojs hono

• CVE-2026-27700 Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo High 8.2
• CVE-2026-22818 JWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback) High 8.2
• CVE-2025-62610 Hono Improperly Authorizes JWT Audience Validation High 8.1
• CVE-2026-29045 Hono: Arbitrary file access via serveStatic vulnerability High 7.5
• CVE-2025-58362 Hono contains a flaw in URL path parsing, potentially leading to path confusion High 7.5

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-f67f-6cw9-8mq4, MINI-6ghf-5jv7-7c63, MINI-j3rq-vc8m-7cw6.