Hono vulnerable to arbitrary file access via serveStatic vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-29045: 0.59% estimated exploitation activity in the next 30 days; percentile 48.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When using serveStatic together with route-based middleware protections (e.g. app.use('/admin/', ...)), inconsistent URL decoding allowed protected static resources to be accessed without authorization. The router used decodeURI, while serveStatic used decodeURIComponent. This mismatch allowed paths containing encoded slashes (%2F) to bypass middleware protections while still resolving to the intended filesystem path. Details The routing layer preserved %2F as a literal string, while serveStatic decoded it into / before resolving the file path. Example: Request: /admin%2Fsecret.html - Router sees: /admin%2Fsecret.html → does not match /admin/ - Static handler resolves: /admin/secret.html As a result, static files under the configured static root could be served without triggering route-based protections. This only affects applications that both: - Protect subpaths using route-based middleware, and - Serve files from the same static root using serveStatic. This does not allow…

Published by the source

4 Mar 2026, 19:48 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-q5qw-h33p-qvwr

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-q5qw-h33p-qvwr

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# Patch Next advisory brief: CVE-2026-29045

Advisory: Hono vulnerable to arbitrary file access via serveStatic vulnerability
IDs: CVE-2026-29045, GHSA-q5qw-h33p-qvwr
Record: https://patchnext.com/advisories/cve-2026-29045 (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected < 4.12.4; fixed in 4.12.4

## Suggested inspection (read-only)
- `npm ls hono --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on hono.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-q5qw-h33p-qvwr (OSV record GHSA-q5qw-h33p-qvwr lists affected ranges: npm hono >=0 <4.12.4 (fixed))
- Verified: https://github.com/advisories/GHSA-q5qw-h33p-qvwr (GitHub-reviewed advisory GHSA-q5qw-h33p-qvwr lists affected ranges: npm hono >=0 <4.12.4)

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