JWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback)
cve-program · CVE-2026-22818
PublishedHono 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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
Read the publisher's advisoryeuvd · EUVD-2026-2017
PublishedHono 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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
Read the publisher's advisorynvd · CVE-2026-22818
PublishedHono 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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
Read the publisher's advisoryosv · GHSA-3vhc-576x-3qv4
Published## 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 tokens to be accepted. ## Details When verifying JWTs using JWKs or a JWKS endpoint, the middleware selected the verification algorithm based on the JWK’s `alg` field if present. If the JWK did not specify an algorithm, the middleware fell back to using the `alg` value provided in the unverified JWT header. Because the `alg` field in a JWK is optional and commonly omitted in real-world JWKS configurations, this behavior could allow an attacker to influence which algorithm is used for verification. In some environments, this may result in authentication or authorization bypass through crafted JWTs. The practical impact depends on application configuration, including which algorithms are accepted and how JWTs are used to make authorization decisions. ## Impact In affected configurations, an attacker may be able to forge JWTs with attacker-controlled claims, potentially leading to authentication or authorization bypass. Applications that do not use the JWK/JWKS middleware, do not rely on JWT-based authentication, or explicitly restrict allowed algorithms are not affected. ## Resolution Update to the latest patched release. **Breaking change:** The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. Instead, callers must explicitly specify which asymmetric algorithms are permitted, and only tokens signed with those algorithms will be accepted. This prevents JWT algorithm confusion by ensuring that algorithm selection is fully controlled by application configuration. As part of this fix, the `alg` option is now required when using the JWK/JWKS middleware, and symmetric (HS*) algorithms are no longer accepted in this context. ### Before (vulnerable configuration) ```ts import { jwk } from 'hono/jwk' app.use( '/auth/*', jwk({ jwks_uri: 'https://example.com/.well-known/jwks.json', // alg was optional }) ) ``` ### After (patched configuration) ```ts import { jwk } from 'hono/jwk' app.use( '/auth/*', jwk({ jwks_uri: 'https://example.com/.well-known/jwks.json', alg: ['RS256'], // required: explicit asymmetric algorithm allowlist }) ) ```
Read the publisher's advisoryAffected versions, risk and source history
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cve-program · CVE-2026-22818
PublishedJWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback)
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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
- Source published
- 13 Jan 2026 19:49:52 UTC
- Source modified
- 15 Jan 2026 15:29:39 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
euvd · EUVD-2026-2017
PublishedHono 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 algorithm specified in the JWT header to influence signature v…
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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
Additional publisher context
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: Jan 13, 2026, 7:49:52 PM
dateUpdated: Jan 15, 2026, 3:29:39 PM
1 related source bulletins · separate from aliases
WID-SEC-W-2026-0328: IBM App Connect Enterprise Certified Container: Mehrere Schwachstellen
CVE-2025-13491 · CVE-2025-61727 · CVE-2025-61729 · CVE-2026-0621 · CVE-2026-21226 · CVE-2026-22817 · CVE-2026-22818
- Source published
- Jan 13, 2026, 7:49:52 PM (timezone not stated)
- Source modified
- Jan 15, 2026, 3:29:39 PM (timezone not stated)
- Saved here
- 15 Nov 2026 07:35:36 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
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EUVD CVSS 3.1 · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
nvd · CVE-2026-22818
PublishedHono 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 algorithm specified in the JWT header to influence signature v…
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 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 tokens to be accepted. The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. This vulnerability is fixed in 4.11.4.
Additional publisher context
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Analyzed
Weakness classifications: CWE-347
Original publisher date fields
published: 2026-01-13T20:16:11.740
lastModified: 2026-06-17T10:20:29.070
1 source CPE criteria · context only
- cpe:2.3:a:hono:hono:*:*:*:*:*:node.js:*:*
The original JSON retains the logical configuration operators, exclusions and version bounds.
- Source published
- 13 Jan 2026 20:16:11 UTC
- Source modified
- 17 Jun 2026 10:20:29 UTC
- Saved here
- 25 Oct 2026 05:17:36 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · [email protected] · Secondary · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
osv · GHSA-3vhc-576x-3qv4
PublishedHono 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 tokens to be accepted. ## Details When verifying JWTs using JWKs or a JWKS endpoint, the middleware selected the verification algorithm based on the JWK’s `alg` field if present. If the JWK did not specify an algorithm, the middleware fell back to using the `alg` value provided in the unverified JWT header. Because the `alg` field in a JWK is optional and commonly omitted in real-world JWKS configurations, this behavior could allow an attacker to influence which algorithm is used for verification. In some environments, this may result in authentication or authorization bypass through crafted JWTs. The practical impact depends on application configuration, including which algorithms are accepted and how JWTs are used to make authorization decisions. ## Impact In affected configurations, an attacker may be able to forge JWTs with attacker-controlled claims, potentially leading to authentication or authorization bypass. Applications that do not use the JWK/JWKS middleware, do not rely on JWT-based authentication, or explicitly restrict allowed algorithms are not affected. ## Resolution Update to the latest patched release. **Breaking change:** The JWK/JWKS JWT verification middleware has been updated to require an explicit allowlist of asymmetric algorithms when verifying tokens. The middleware no longer derives the verification algorithm from untrusted JWT header values. Instead, callers must explicitly specify which asymmetric algorithms are permitted, and only tokens signed with those algorithms will be accepted. This prevents JWT algorithm confusion by ensuring that algorithm selection is fully controlled by application configuration. As part of this fix, the `alg` option is now required when using the JWK/JWKS middleware, and symmetric (HS*) algorithms are no longer accepted in this context. ### Before (vulnerable configuration) ```ts import { jwk } from 'hono/jwk' app.use( '/auth/*', jwk({ jwks_uri: 'https://example.com/.well-known/jwks.json', // alg was optional }) ) ``` ### After (patched configuration) ```ts import { jwk } from 'hono/jwk' app.use( '/auth/*', jwk({ jwks_uri: 'https://example.com/.well-known/jwks.json', alg: ['RS256'], // required: explicit asymmetric algorithm allowlist }) ) ```
- Source published
- 13 Jan 2026 21:52:03 UTC
- Source modified
- 10 Sep 2026 03:50:58 UTC
- Saved here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
Publisher rating · HIGH