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Medium · 5.9 CVE-2026-54286 EUVD-2026-38327GHSA-wwfh-h76j-fc44

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

Published Jun 22, 2026 · Updated Jun 23, 2026 · Assigned by GitHub_M

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.

Affected products

VendorProductAffectedFixed
honojs hono < 4.12.25 —

Affected packages

EcosystemPackageAffectedFixedRecord
npm hono < 4.12.25 4.12.25 GHSA-wwfh-h76j-fc44

Advisories 1

References