toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype

Exploitation

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

CVSS 4.0

8.8 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-114142: 0.51% estimated exploitation activity in the next 30 days; percentile 43.62 (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 CVE-2026-63376 described prototype pollution through proto key-path desynchronization and was fixed in 4.1.2 by rewriting the path bookkeeping and adding an ownedContainers WeakSet. The desynchronization is still reachable, spelled with a quote character instead of a dot, and the owned-container check is not applied on the path that matters. A four-line TOML document parsed with toml.parse() writes a property onto Object.prototype, where it is visible to every object in the process — including objects produced by unrelated libraries.

Details Three gaps compose. All line numbers are `lib/compiler.js` in 5.0.0. 1. The path-key encoding is ambiguous. `quoteDottedString()` quotes a segment only when it contains a `.`, and never escapes a `"` inside the segment: ```js 287: function quoteDottedString(str) { 288: if (str.indexOf(".") > -1) { 289: return "\"" + str + "\""; 290: } else { 291: return str; 292: } 293: } ``` So the key path `['x.y']` and the key path…

Published by the source

22 Oct 2026, 16:39 UTC

Last modified by the source

26 Oct 2026, 14:45 UTC

Source last checked

27 Oct 2026, 06:00 UTC

1. Revision 6 · amended · 27 Oct 2026

   Amended from osv record GHSA-h895-cgqg-jf52

2. Revision 5 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-h895-cgqg-jf52

3. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-h895-cgqg-jf52

4. Revision 3 · amended · 24 Oct 2026

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

5. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-h895-cgqg-jf52

6. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-h895-cgqg-jf52

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# Patch Next advisory brief: CVE-2026-114142

Advisory: toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype
IDs: CVE-2026-114142, GHSA-h895-cgqg-jf52
Record: https://patchnext.com/advisories/cve-2026-114142 (revision 6, source checked 27 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: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: toml 5.0.1; tome 5.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm toml: affected < 5.0.1; fixed in 5.0.1
- npm tome: affected <= 5.0.0; fixed in 5.0.1

## Suggested inspection (read-only)
- `npm ls toml --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls tome --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 toml, tome.
- 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-h895-cgqg-jf52 (GitHub-reviewed advisory GHSA-h895-cgqg-jf52 lists affected ranges: npm tome >=0 <=5.0.0)
- Verified: https://osv.dev/vulnerability/GHSA-h895-cgqg-jf52 (OSV record GHSA-h895-cgqg-jf52 lists affected ranges: npm tome >=0 <5.0.1 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-h895-cgqg-jf52 (OSV record GHSA-h895-cgqg-jf52 lists affected ranges: npm toml >=0 <5.0.1 (fixed))

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