Forge: Prototype Pollution in forge.http cookie handling via a malicious Set-Cookie

Exploitation

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

CVSS

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

EPSS

• CVE-2026-118777: 0.26% estimated exploitation activity in the next 30 days; percentile 17.18 (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 The `forge.http` client stored cookies from `Set-Cookie` response headers in a plain object keyed by cookie name and path. A malicious server could use the cookie name `proto` to add properties to `Object.prototype`, use inherited names such as `constructor` to add properties to `Object`, and send an empty cookie value to delete `Object.prototype` properties. Fixed in node-forge 1.4.1.

Details `client.setCookie()` in `lib/http.js` stored a cookie with `client.cookies[cookie.name][cookie.path] = cookie`, creating `client.cookies[cookie.name]` only when `!(cookie.name in client.cookies)`. Both values come from the server's `Set-Cookie` header via `response.getCookies()`. Because `in` also sees inherited properties: - a cookie named `proto` skipped the initialization, `client.cookies['proto']` returned `Object.prototype`, and the cookie path was written as a new `Object.prototype` property, visible on every object; - a cookie named `constructor` wrote onto…

Published by the source

30 Oct 2026, 23:02 UTC

Last modified by the source

30 Oct 2026, 23:15 UTC

Source last checked

31 Oct 2026, 06:00 UTC

1. Revision 2 · amended · 31 Oct 2026

   Amended from osv record GHSA-6wvx-3r32-xmcg

2. Revision 1 · created · 30 Oct 2026

   Published from ghsa record GHSA-6wvx-3r32-xmcg

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# Patch Next advisory brief: CVE-2026-118777

Advisory: Forge: Prototype Pollution in forge.http cookie handling via a malicious Set-Cookie
IDs: CVE-2026-118777, GHSA-6wvx-3r32-xmcg
Record: https://patchnext.com/advisories/cve-2026-118777 (revision 2, source checked 31 Oct 2026, 06:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: node-forge 1.4.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm node-forge: affected < 1.4.1; fixed in 1.4.1

## Suggested inspection (read-only)
- `npm ls node-forge --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 node-forge.
- 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-6wvx-3r32-xmcg (GitHub-reviewed advisory GHSA-6wvx-3r32-xmcg lists affected ranges: npm node-forge >=0 <=1.4.0)
- Verified: https://osv.dev/vulnerability/GHSA-6wvx-3r32-xmcg (OSV record GHSA-6wvx-3r32-xmcg lists affected ranges: npm node-forge >=0 <1.4.1 (fixed))

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