{"id":"CVE-2026-50029","summary":"js-toml has silent type confusion via falsy-primitive duplicate-key bypass","details":"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 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.","aliases":["GHSA-m34p-749j-x6m6"],"modified":"2026-08-19T03:31:16.039180502Z","published":"2026-08-14T19:08:54.941Z","database_specific":{"cwe_ids":["CWE-697"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50029.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/sunnyadn/js-toml/releases/tag/v1.1.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50029.json"},{"type":"ADVISORY","url":"https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-50029"},{"type":"FIX","url":"https://github.com/sunnyadn/js-toml/commit/e0504fa5d3dcde2d1d588c9001c24b7b700beeeb"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/sunnyadn/js-toml","events":[{"introduced":"0"},{"fixed":"e0504fa5d3dcde2d1d588c9001c24b7b700beeeb"},{"fixed":"e3041b298259e8980c85085a84ae0ffdfd4e51f9"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.1.2"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v1.1.1","v1.1.0","v1.0.3","v1.0.2","v1.0.1","v1.0.0","v0.1.1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50029.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}