js-toml Prototype Pollution Vulnerability
Date: 2025-08
Affected: npm/js-toml
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2025-54803
CWE: CWE-1321

A prototype pollution vulnerability in `js-toml` allows a remote attacker to add or modify properties of the global `Object.prototype` by parsing a maliciously crafted TOML input. ### Impact The `js-toml` library is vulnerable to Prototype Pollution. When parsing a TOML string containing the specially crafted key `__proto__`, an attacker can add or modify properties on the global `Object.prototype`. While the `js-toml` library itself does not contain known vulnerable "gadgets", this can lead to severe security vulnerabilities in applications that use the library. For example, if the consuming application checks for the existence of a property for authorization purposes (e.g., `user.isAdmin`), this vulnerability could be escalated to an authentication bypass. Other potential impacts in the application include Denial of Service (DoS) or, in some cases, Remote Code Execution (RCE), depending on the application's logic and dependencies. Any application that uses an affected version of `js-toml` to parse untrusted input is vulnerable. The severity of the impact, ranging from unexpected behavior to a full security compromise, is dependent on the application's specific code and its handling of object properties. ### Patches This vulnerability has been patched in version `1.0.2`. All users are advised to upgrade to version `1.0.2` or later to mitigate this issue. Users of all prior versions are affected. ### Workarounds If you are unable to upgrade to a patched version, the


Mitigations:

Architectural layers (MAESTRO):