Hono JWK Auth Middleware has JWT algorithm confusion when JWK lacks "alg" (untrusted header.alg fallback)

Summary A flaw in Hono’s JWK/JWKS JWT verification middleware allowed the algorithm specified in the JWT header to influence signature verification when the selected JWK did not explicitly define an algorithm. This could enable JWT algorithm confusion and, in certain configurations, allow forged...

CVE-2026-22818

CVE-2026-22818 concerns Hono’s JWK/JWKS JWT verification middleware. Prior to 4.11.4, if a JWK did not explicitly specify an algorithm, the middleware could derive the signature verification algorithm from the untrusted JWT header’s alg value, enabling algorithm confusion and potentially forged t...