sunnyadn js-toml up to 1.1.1 Duplicate Key State Machine load type confusion

Summaryinfo

A vulnerability marked as problematic has been reported in sunnyadn js-toml up to 1.1.1. Affected by this vulnerability is the function Load of the component Duplicate Key State Machine. Performing a manipulation results in type confusion. This vulnerability was named CVE-2026-50029. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in sunnyadn js-toml up to 1.1.1. It has been classified as problematic. This affects the function load of the component Duplicate Key State Machine. The manipulation with an unknown input leads to a type confusion vulnerability. CWE is classifying the issue as CWE-843. The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type. This is going to have an impact on integrity. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-50029 since 06/03/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

Upgrading to version 1.1.2 eliminates this vulnerability.

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Productinfo

Vendor

• sunnyadn

Name

• js-toml

Version

• 1.1.0
• 1.1.1

Website

• Product: https://github.com/sunnyadn/js-toml/

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