# CVE-2026-63386: js-toml stack exhaustion in recursive parser

Source: https://junglewise.ai/threats/cve-2026-63386-js-toml-is-a-toml-parser-for-javascript-prior-to-1-1-3-load-does  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-63386 · Severity: medium · CVSS 5.3 · Published 2026-09-22

js-toml is a JavaScript library for parsing TOML configuration files. A flaw in versions before 1.1.3 allows attacker-controlled input with deeply nested structures to crash the parser by exhausting the call stack, causing denial of service to applications that rely on it.

Technologies: [Sunnyadn Js-Toml](https://junglewise.ai/threats/technologies/js-toml). Vendors: [Sunnyadn](https://junglewise.ai/threats/vendors/sunnyadn).

## Quick answers

**Is CVE-2026-63386 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63386 being exploited in the wild.

**How severe is CVE-2026-63386?** Medium severity, with a CVSS score of 5.3, published 22 September 2026.

**Which products and versions are affected?** Sunnyadn Js-Toml before 1.1.3.

**Is there a fix for CVE-2026-63386?** A patch was published on 2026-06-30. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63386 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63386?** Check whether you run Sunnyadn Js-Toml at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The recursive parser and interpreter in js-toml do not bound nesting depth for arrays, inline tables, or dotted keys, allowing deeply nested or complex input to exhaust the V8 call stack and throw an uncaught RangeError instead of the documented SyntaxParseError. Applications that parse untrusted TOML and only catch SyntaxParseError will propagate the unexpected exception, terminating the process. Version 1.1.3 adds configurable recursion depth limits (default 100) and converts residual RangeErrors to SyntaxParseError.

## Affected products

- sunnyadn js-toml before 1.1.3

## Timeline

- 2026-09-22: disclosed
- 2026-06-30: patched

## References

- [https://github.com/sunnyadn/js-toml/commit/4e10acf1f99ff3cb443c58b8f0a57664e41e87c6](https://github.com/sunnyadn/js-toml/commit/4e10acf1f99ff3cb443c58b8f0a57664e41e87c6)
- [https://github.com/sunnyadn/js-toml/releases/tag/v1.1.3](https://github.com/sunnyadn/js-toml/releases/tag/v1.1.3)

## Related threats

- [sunnyadn js-toml type confusion via duplicate-key bypass](https://junglewise.ai/threats/cve-2026-50029-sunnyadn-js-toml-type-confusion-via-duplicate-key-bypass)
- [js-toml CPU exhaustion via O(n²) BigInt construction](https://junglewise.ai/threats/cve-2026-49293-js-toml-cpu-exhaustion-via-o-n-bigint-construction)