CVE-2026-47676 Hono: app.mount() strips mount prefix using undecoded path, causing incorrect routing for percent-encoded paths
Attackers can cause incorrect routing in mounted sub-applications by using percent-encoded paths, potentially bypassing intended access controls or logic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47676?
CVE-2026-47676 is a medium-severity vulnerability in honojs hono, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, app.mount() strips the mount prefix from the incoming request path using the raw URL pathname, while route matching is performed against the percent-decoded path. This inconsistency causes the prefix to be stripped at the wrong position when the path contains percent-encoded multi-byte characters, resulting in the mounted sub-application receiving an incorrect path. This vulnerability is fixed in 4.12.21.
Which versions are affected by CVE-2026-47676?
2 open source packages ship an affected version, including hono. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | All versions | 4.12.21 |
hono npm | All versions | 4.12.21 |
Products include Hono Hono.
How do I fix CVE-2026-47676?
Upgrade hono to 4.12.21 or later.
Is CVE-2026-47676 being exploited?
There is no known exploitation of CVE-2026-47676 in the wild and no public exploit code.
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- CVE-2026-22818 JWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback)
- CVE-2025-62610 Hono Improperly Authorizes JWT Audience Validation
- CVE-2026-29045 Hono: Arbitrary file access via serveStatic vulnerability
Sources
Also known as ECHO-22d9-65f9-d2a1, GHSA-2gcr-mfcq-wcc3, MINI-44c8-22vw-9qxr, MINI-68j6-g2pc-r6r9, MINI-88gj-fxv3-3rf6, MINI-c296-vr9p-2gfh and 8 more.