CVE-2026-54286CWE-22

Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)

Medium · published June 22, 2026

CVSS v3.1
5.9
EPSS
0%
Percentile
36.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00433 · 36.6th percentile
Weakness
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Published
2026-06-22T17:14Z
EPSS history
Timeline
  • 22 JUN 17:14Z
    Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)
    cvelistv5