CVE-2026-50029 is a medium-severity security vulnerability in js-toml (npm), affecting versions <= 1.1.1. It is fixed in 1.1.2.
Summary js-toml's 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. Details Two truthy checks are wrong: src/load/interpreter.ts:214, Interpreter.tryCreatingObject src/load/interpreter.ts:278, Interpreter.getOrCreateArray Both should use the in operator. Containers are created via Object.create(null), so in is unambiguous (no inherited keys to worry about). The bug is reachable through every parent-walking interpreter path: assignValue, dotted keys in key = value createTable, [stdTable] headers getOrCreateArray, [[arrayOfTables]] headers PoC Impact Spec-violating input acceptance leading to structural type confusion. (CWE-697) Suggested fix in src/load/interpreter.ts
CVE-2026-50029 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.1.2). Upgrading removes the vulnerable code path.
npm
js-toml (<= 1.1.1)js-toml → 1.1.2 (npm)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Already deployed Kodem? See CVE-2026-50029 in your environment →Upgrade js-toml to 1.1.2 or later to resolve this vulnerability.
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CVE-2026-50029 is a medium-severity security vulnerability in js-toml (npm), affecting versions <= 1.1.1. It is fixed in 1.1.2.
CVE-2026-50029 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
js-toml (npm) versions <= 1.1.1 is affected.
Yes. CVE-2026-50029 is fixed in 1.1.2. Upgrade to this version or later.
Whether CVE-2026-50029 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade js-toml to 1.1.2 or later.