toml-node is a TOML parser for Node.js and the browser. Prior to 4.2.0, toml.parse() uses a Peggy 5.1.0 generated recursive-descent parser in lib/parser.js whose peg$parsevalue, peg$parsearray, and peg$parseinline_table_entry functions recurse through nested arrays and inline tables without a depth limit. A remote unauthenticated application parsing an attacker-controlled TOML document containing a few thousand nested arrays or inline tables can exhaust the Node.js call stack, raise an unexpected RangeError rather than the parser's SyntaxError, and terminate an unprotected request worker or process. The corresponding grammar source is src/toml.pegjs, where the generated parser must be bounded. This issue is fixed in version 4.2.0.

Affected: npm: toml

### Summary

`toml.parse()` crashes with an uncaught `RangeError: Maximum call stack size exceeded` when parsing deeply nested arrays or inline tables. The parser is generated by **Peggy 5.1.0** (a PEG parser generator) as a recursive-descent parser; the value rule mutually recurses with the array and inline-table rules with **no depth limit**, so nesting depth equal to the input depth exhausts Node's call stack.

A small payload — a bare array nested a few thousand levels deep (**~5–6 KB**) — reliably crashes the process on a default Node.js configuration. `toml` has **~47 million monthly downloads**.

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## Vulnerable Code

The parser is a **generated** recursive-descent parser (`lib/parser.js`, header: `// @generated by Peggy 5.1.0.`). The recursion sink is the mutual recursion between the `value`, `array`, and `inline_table` rule functions — none carry a depth counter:

```javascript // lib/parser.js — peg$parsevalue() @ line 1008 function peg$parsevalue() { ... s0 = peg$parsearray(); // line 1017 ← value → array if (s0 === peg$FAILED) { s0 = peg$parseinline_table(); // line 1019 ← value → inline_table } ... }

// peg$parsearray() @ line 2879 function peg$parsearray() { ... s3 = peg$parsevalue(); // line 2931 ← array element → value (back-edge) ... }

// peg$parseinline_table() @ line 3066 → peg$parseinline_table_entry() @ line 3239 function peg$parseinline_table_entry() { ... s5 = peg$parsevalue(); // line 3266 ←…