Medium severity · published Jun 22, 2026
CVE-2026-54286
Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)
5.9
CVSS
0.4%
EPSS
No
On KEV
Description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.25, on Windows hosts, an encoded backslash (%5C) in the request path decodes to \, which the Windows path resolver treats as a separator. serve-static then resolves a single URL segment such as admin\secret.txt into a nested file under the root and serves it, letting an attacker read static files meant to be protected behind prefix-mounted middleware. This vulnerability is fixed in 4.12.25.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HO
hono · honojs
< 4.12.25 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-54286
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-54286
github.com
https://github.com/honojs/hono/security/advisories/GHSA-wwfh-h76j-fc44
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