Medium severity · published Apr 8, 2026
CVE-2026-39407
Hono has a middleware bypass via repeated slashes in serveStatic
5.3
CVSS
0.5%
EPSS
No
On KEV
Description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path. When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass. This vulnerability is fixed in 4.12.12.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HO
hono · honojs
< 4.12.12 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39407
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39407
Patch
https://github.com/honojs/hono/commit/9aff14bd727f8b0435c963363fd803260e7b8e3c
Release Notes
https://github.com/honojs/hono/releases/tag/v4.12.12
Vendor Advisory
https://github.com/honojs/hono/security/advisories/GHSA-wmmm-f939-6g9c
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