Node.js Adapter for Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Fixed
No CVSS vector from any source. Fix status from GitHub.
Summary
The same as the `hono` core [Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)](https://github.com/honojs/hono/security/advisories/GHSA-wwfh-h76j-fc44). ### Summary 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. Directory escape (`..`) remains blocked. ### Details The router splits paths only on `/`, so `/admin%5Csecret.txt` is one segment and middleware on `/admin/*` does not run. The `serve-static` guard rejects `.`/`..` and consecutive separators but lets a lone `\` through; on Windows the file resolver re-splits it into the protected subtree. This affects Windows hosts serving static files via the Node, Bun, or Deno adapters that guard a static subtree with prefix-mounted middleware. ### Impact An unauthenticated attacker can read static files under a middleware-guarded prefix on Windows hosts. The read stays within the configured root; escape outside the root is not possible.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | @hono/node-server (npm) | 2.0.0 to before 2.0.5 | 2.0.5 | Patch available | GHSA-frvp-7c67-39w9 |
| — | @hono/node-server (npm) | before 1.19.15 | 1.19.15 | Patch available | GHSA-frvp-7c67-39w9 |
- @hono/node-server (npm) Vendor— Affected 2.0.0 to before 2.0.5 Fixed in 2.0.5 Patch available GHSA-frvp-7c67-39w9
- @hono/node-server (npm) Vendor— Affected before 1.19.15 Fixed in 1.19.15 Patch available GHSA-frvp-7c67-39w9
Remediation
- Fix · GHSA-frvp-7c67-39w9 @hono/node-server (npm) Fixed in 2.0.5 Advisory →
- Fix · GHSA-frvp-7c67-39w9 @hono/node-server (npm) Fixed in 1.19.15 Advisory →
Timeline
- 2026-10-03 Threatist record created from GHSA-frvp-7c67-39w9
References
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences