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Medium, CVSS 4.3amended

scim-patch: Mutation of Inherited Built-in Method Objects

CVE-2026-61834GHSA-2mhw-wcx5-v3xj

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (scim-patch 0.9.2), 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

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
EPSS
  • CVE-2026-61834: 0.40% estimated exploitation activity in the next 30 days; percentile 33.84 (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 Incomplete Prototype Pollution Fix Allows Mutation of Inherited Built-in Method Objects scim-patch blocks direct dangerous path segments such as proto, constructor, and prototype, but still traverses inherited properties when applying SCIM patch paths. An attacker who controls a SCIM PATCH operation can use paths such as toString.polluted to mutate shared built-in function objects, for example Object.prototype.toString. Impact A malicious patch can add attacker-controlled properties to inherited built-in method objects. The impact is narrower than direct Object.prototype pollution, but the mutation is process-global and may affect application logic that reads properties from inherited methods. Details Affected code paths: - navigate() reads inherited properties via schema[subPath] - assign() uses key in obj, which treats inherited properties as existing Because inherited keys are followed, safe-looking path segments such as toString can resolve to shared built-in objects. PoC…

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

    Amended from ghsa record GHSA-2mhw-wcx5-v3xj

  2. Revision 2 · amended ·

    Amended from osv record GHSA-2mhw-wcx5-v3xj

  3. Revision 1 · created ·

    Published from ghsa record GHSA-2mhw-wcx5-v3xj

Agent brief

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# Patch Next advisory brief: CVE-2026-61834

Advisory: scim-patch: Mutation of Inherited Built-in Method Objects
IDs: CVE-2026-61834, GHSA-2mhw-wcx5-v3xj
Record: https://patchnext.com/advisories/cve-2026-61834 (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: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: scim-patch 0.9.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm scim-patch: affected < 0.9.2; fixed in 0.9.2

## Suggested inspection (read-only)
- `npm ls scim-patch --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 scim-patch.
- 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-2mhw-wcx5-v3xj (GitHub-reviewed advisory GHSA-2mhw-wcx5-v3xj lists affected ranges: npm scim-patch >=0 <0.9.2)
- Verified: https://osv.dev/vulnerability/GHSA-2mhw-wcx5-v3xj (OSV record GHSA-2mhw-wcx5-v3xj lists affected ranges: npm scim-patch >=0 <0.9.2 (fixed))

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