{"id":"CVE-2026-50029","title":"js-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with `if (object[key])` instead of `if (key in object)`","summary":"js-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with `if (object[key])` instead of `if (key in object)`. When the prior value is a falsy pri…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-697"],"vendor":"js-toml","product":"js-toml","affected":["js-toml <= 1.1.1"],"patched":["js-toml 1.1.2"],"published":"2026-08-14","updated":"2026-09-18","sourceUpdated":"2026-09-18T20:09:01.757","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-50029","references":[{"url":"https://github.com/sunnyadn/js-toml/commit/e0504fa5d3dcde2d1d588c9001c24b7b700beeeb","label":"security-advisories@github.com"},{"url":"https://github.com/sunnyadn/js-toml/releases/tag/v1.1.2","label":"security-advisories@github.com"},{"url":"https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6","label":"security-advisories@github.com"},{"url":"https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://github.com/advisories/GHSA-m34p-749j-x6m6"}],"tags":["nvd","ghsa","npm"],"epss":0.00232,"epssPercentile":0.14398,"ecosystem":"npm","ingestedAt":"2026-06-29T13:24:35.091Z","slug":"CVE-2026-50029","body":"## Overview\n\njs-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with `if (object[key])` instead of `if (key in object)`. When the prior value is a falsy primitive — `false`, `0`, `0n`, `0.0`, `-0`, or `\"\"` — the duplicate-key branch is skipped and the value is silently overwritten by a later sub-table, dotted-key sub-table, or array-of-tables sharing the same name. Per the TOML 1.0.0 spec (\"Defining a key multiple times is invalid\"; \"You cannot define any key or table more than once\"), this should be a parse error. The result is structural type confusion of attacker-named keys in the value returned by `load()`. A boolean-typed `false` (or numeric `0`) becomes a truthy object. Host applications that gate behavior on `if (config.flag)`, `if (!user.banned)`, `if (config.allowDelete)`, or `if (config.publicMode)` will silently take the truthy branch. This is distinct from GHSA-65fc-cr5f-v7r2 (the 1.0.2 prototype-pollution fix). `Object.prototype` is not polluted. The `Object.create(null)` mitigation from 1.0.2 is intact; the bug here is in the duplicate-key state machine, not in container construction. Version 1.1.2 patches the incorrect comparison.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-50029)\n\nAffected packages:\n\n- `js-toml <= 1.1.1`\n\nPatched in:\n\n- `js-toml 1.1.2`\n\nSource: https://github.com/advisories/GHSA-m34p-749j-x6m6","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}