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Low, CVSS 3.7amended

joi: object().rename() with a template target can set the validated object's prototype

CVE-2026-84367GHSA-gg4h-3hg2-grpc

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (joi 18.2.4, 17.13.5), 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 joi

    Affected
    >= 16.0.0, < 17.13.5>= 18.0.0, < 18.2.4
    Fixed in
    17.13.5, 18.2.4

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS
  • CVE-2026-84367: 0.39% estimated exploitation activity in the next 30 days; percentile 33.07 (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.

Impact Applications are affected only if a schema renames keys with a regular-expression source and a Joi.expression() / Joi.x() target that interpolates the pattern's own match data, combined with { multiple: true }, for example .rename(/^x-(.+)$/, Joi.x('{#1}'), { multiple: true }). Because the target is rendered from the matched input key, an attacker who controls input keys can send x-proto with an object value and make the rename target render as proto, which sets the prototype of the object joi returns instead of creating a key on it. The global Object.prototype is not modified, so the effect is confined to the object returned by that one validate() call. Schemas using a static string rename target are not affected, and neither are schemas left on the default { multiple: false }. Patches Versions 17.13.5 and 18.2.4 have been released to address the issue. Workarounds 1. Replace the template rename target with a static string target. 2. Keep the template but make the capture…

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

    Amended from ghsa record GHSA-gg4h-3hg2-grpc

  2. Revision 2 · amended ·

    Amended from osv record GHSA-gg4h-3hg2-grpc

  3. Revision 1 · created ·

    Published from ghsa record GHSA-gg4h-3hg2-grpc

Agent brief

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# Patch Next advisory brief: CVE-2026-84367

Advisory: joi: object().rename() with a template target can set the validated object's prototype
IDs: CVE-2026-84367, GHSA-gg4h-3hg2-grpc
Record: https://patchnext.com/advisories/cve-2026-84367 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: joi 18.2.4, 17.13.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm joi: affected >= 16.0.0, < 17.13.5; >= 18.0.0, < 18.2.4; fixed in 17.13.5, 18.2.4

## Suggested inspection (read-only)
- `npm ls joi --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 joi.
- 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://github.com/advisories/GHSA-gg4h-3hg2-grpc (GitHub-reviewed advisory GHSA-gg4h-3hg2-grpc lists affected ranges: npm joi >=16.0.0 =18.0.0 <18.2.4)
- Verified: https://osv.dev/vulnerability/GHSA-gg4h-3hg2-grpc (OSV record GHSA-gg4h-3hg2-grpc lists affected ranges: npm joi >=16.0.0 =18.0.0 <18.2.4 (fixed))

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