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Medium, CVSS 5.9amended

Hono: Path traversal in toSSG() allows writing files outside the output directory

CVE-2026-39408GHSA-xf4j-xp2r-rqqx

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (hono 4.12.12), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm hono

    Affected
    >= 4.0.0, <= 4.12.11
    Fixed in
    4.12.12

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.9 · CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-39408: 0.50% estimated exploitation activity in the next 30 days; percentile 43.13 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary A path traversal issue in toSSG() allows files to be written outside the configured output directory during static site generation. When using dynamic route parameters via ssgParams, specially crafted values can cause generated file paths to escape the intended output directory. Details The static site generation process creates output files based on route paths derived from application routes and parameters. When ssgParams is used to provide values for dynamic routes, those values are used to construct output file paths. If these values contain traversal sequences (e.g. ..), the resulting output path may resolve outside the configured output directory. As a result, files may be written to unintended locations instead of being confined within the specified output directory. For example: In this case, the generated output path may resolve outside ./static, resulting in a file being written outside the intended output directory. Impact An attacker who can influence values…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-xf4j-xp2r-rqqx

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-xf4j-xp2r-rqqx

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-39408

Advisory: Hono: Path traversal in toSSG() allows writing files outside the output directory
IDs: CVE-2026-39408, GHSA-xf4j-xp2r-rqqx
Record: https://patchnext.com/advisories/cve-2026-39408 (revision 3, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.12. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected >= 4.0.0, <= 4.12.11; fixed in 4.12.12

## 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-xf4j-xp2r-rqqx (OSV record GHSA-xf4j-xp2r-rqqx lists affected ranges: npm hono >=4.0.0 <4.12.12 (fixed))
- Verified: https://github.com/advisories/GHSA-xf4j-xp2r-rqqx (GitHub-reviewed advisory GHSA-xf4j-xp2r-rqqx lists affected ranges: npm hono >=4.0.0 <=4.12.11)

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