CVE-2026-50029

Technical Description

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 prototy

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References