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Response snapshot Oct 27, 2026, 02:47 UTC

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VulnerabilityCVE-2026-114142

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

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. **1. The path-key encoding is ambiguous.

Published Updated

At a glance

Exploited
Not known
Severity
8.8 High (CVSS 4.0)
Chance of exploitation
0.4% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: tome: 5.0.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-h895-cgqg-jf52 (opens a new tab)

What happened

### 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:

Continue reading

```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 `['"x', 'y"']` both render as the string `"x.y"`. This is the same desynchronization CVE-2026-63376 named, with a quote in place of the dot.

**2. A table-array header can clear another key's guard.** `addTableArray()` walks `assignedPaths` / `valueAssignments` with `isSameOrSubPath()` over those ambiguous strings, so a header whose rendered path collides with an unrelated key deletes that key's entry.

**3. The descent in `assign()` has no owned-container check.** `deepRef()` applies `isOwnedContainer()` only to intermediate segments (`lib/compiler.js:265`, `:273`) and returns the final container unchecked. `assign()` then walks it with only a shape test:

```js 93: target = target[k]; ... 103: target[lastKey] = reduced; ```

A TOML datetime is a `Date`. It satisfies `typeof target[k] === "object"` and is not an array, so the walk descends into it — and a `Date` has a live prototype chain to `Object.prototype`.

Putting the three together, a document can make the current table a `Date` and then walk `__proto__.__proto__` to `Object.prototype`.

```bash mkdir poc && cd poc && npm init -y >/dev/null && npm install toml@5.0.0 ```

```toml # poc.toml "b.c" = 1979-05-27T07:32:00Z [['"b']] ["b.c"] __proto__.__proto__.polluted = "yes" ```

Line 1 defines a key whose rendered path is `"b.c"` and whose value is a `Date`. Line 2 is a table-array header whose rendered path collides with it, clearing its guard. Line 3 re-enters that key, so the current table is now the `Date`. Line 4 walks `Date` → `Date.prototype` → `Object.prototype`.

```js // poc.js const toml = require('toml'); const fs = require('fs');

console.log('before:', JSON.stringify(({}).polluted)); toml.parse(fs.readFileSync('poc.toml', 'utf8')); console.log('after: ', JSON.stringify(({}).polluted)); console.log('Object.prototype.hasOwnProperty("polluted") =', Object.prototype.hasOwnProperty('polluted')); console.log('JSON.parse("{}").polluted =', JSON.stringify(JSON.parse('{}').polluted)); ```

``` $ node poc.js before: undefined after: "yes" Object.prototype.hasOwnProperty("polluted") = true JSON.parse("{}").polluted = "yes" ```

The payload sets a single harmless marker property. The last line shows the property is visible on an object this code never touched.

A useful control: the same document without line 2 (the guard-clearing header) is correctly rejected on 4.1.2 and later, which confirms the clearing step is what is load-bearing.

### Impact

Any application that parses a TOML document from an untrusted source is affected — a configuration file uploaded by a user, a manifest from a third-party package or repository, a document posted to an API. Prototype pollution of this kind commonly escalates to authentication or authorization bypass, denial of service, and in applications with a suitable gadget, remote code execution, because every object in the process inherits the injected property.

Suggested fix: in `assign()`, apply the same check the intermediate descent already uses — after `target = target[k]`, reject when `!isOwnedContainer(target)`. Equivalently, apply `isOwnedContainer` to the value `deepRef()` returns. Separately, `quoteDottedString()` should escape `"` inside a segment so that distinct key paths cannot render to the same string.

Affected package ranges reported by GitHub: tome: <= 5.0.0

Scores and how they were measured

CVSS base severity

8.8

Version 4.0As of

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 33.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-h895-cgqg-jf52 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h895-cgqg-jf52, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    NVD CVE-2026-114142 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  13. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  14. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-114142, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 22). toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype (CVE-2026-114142). https://kevwire.com/record/CVE-2026-114142

MLA

"toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype (CVE-2026-114142)." KEVWire, 22 Oct. 2026, kevwire.com/record/CVE-2026-114142.

Chicago

KEVWire. "toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype (CVE-2026-114142)." Last modified October 22, 2026. https://kevwire.com/record/CVE-2026-114142.

Evidence summary (plain text)

toml-node: Prototype pollution: parsing a TOML document can write to Object.prototype (Oct 22, 2026).
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.

**1. The path-key encoding is ambiguous.** `quoteDottedString()` quotes a segment only when it contains a `.`, and never escapes a `"` inside the segment:
CVSS 8.8 (version 4.0; evidence as of Oct 22, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-114142).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-114142&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-h895-cgqg-jf52: https://github.com/advisories/GHSA-h895-cgqg-jf52
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTowNVrOAAf0JQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0Mzo0NVrOAAf0Iw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0MzozMVrOAAf0Ig%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozMDoyN1rOAAY_5Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODoyOTowNVrOAAfz8g%3D%3D
NVD CVE-2026-114142: https://nvd.nist.gov/vuln/detail/CVE-2026-114142
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=8000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-114142&date=2026-10-26
Record ID: CVE-2026-114142.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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