GHSA-PQHP-25J4-6HQ9

smol-toml has a Denial of Service via malicious TOML document using deeply nested inline tables

An attacker can send a maliciously crafted TOML to cause the parser to crash because of a stack overflow caused by a deeply nested inline structure. A similar problem occurs when attempting to stringify deeply nested objects.

The library does not limit the maximum exploration depth while parsing or producing TOML documents, nor does it offer a way to do so.

Proof of concept

require("smol-toml").parse("e=" + "{e=".repeat(9999) + "{}" + "}".repeat(9999))

Workarounds

Wrap all invocations of parse and stringify in a try/catch block.

Applications which parse arbitrary TOML documents may suffer availability issues if they receive malicious input. If uncaught, the crash may cause the application itself to crash. The impact is deemed minor, as the function is already likely to throw errors on invalid input and therefore to properly handle errors.

Due to the design of most JavaScript runtimes, the uncontrolled recursion does not lead to excessive memory usage and the execution is quickly aborted.

As a reminder, it is strongly advised when working with untrusted user input to expect errors to occur and to appropriately catch them.

GHSA-PQHP-25J4-6HQ9 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 (1.3.1); upgrading removes the vulnerable code path.

Kodem intelligence

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Version 1.3.1 offers a mechanism to limit the exploration depth before halting with a TomlError when parsing, with a default cap of 1000. A same mechanism has been implemented for stringifying objects.

Please note that the parser will still throw an error upon such cases. It is, however, a now-controlled and documented behavior of the library.

1. What is GHSA-PQHP-25J4-6HQ9? GHSA-PQHP-25J4-6HQ9 is a medium-severity security vulnerability in smol-toml (npm), affecting versions <= 1.3.0. It is fixed in 1.3.1.
2. How severe is GHSA-PQHP-25J4-6HQ9? GHSA-PQHP-25J4-6HQ9 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.
3. Which versions of smol-toml are affected by GHSA-PQHP-25J4-6HQ9? smol-toml (npm) versions <= 1.3.0 is affected.
4. Is there a fix for GHSA-PQHP-25J4-6HQ9? Yes. GHSA-PQHP-25J4-6HQ9 is fixed in 1.3.1. Upgrade to this version or later.
5. Is GHSA-PQHP-25J4-6HQ9 exploitable, and should I be worried? Whether GHSA-PQHP-25J4-6HQ9 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
6. What actually determines whether GHSA-PQHP-25J4-6HQ9 is exploitable, and how bad it is? 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.
7. How do I fix GHSA-PQHP-25J4-6HQ9? Upgrade smol-toml to 1.3.1 or later.

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