GHSA-9qmh-m7c6-f92p toml-node: Uncontrolled resource consumption (CPU DoS) via unbounded-length integer literals in toml.parse()

• npm toml: < 5.0.1 → fixed in 5.0.1

Summary `toml.parse()` converts integer literals (hex, octal, binary, and decimal) to `BigInt` without first bounding the length of the digit sequence. Since `BigInt(string)` construction from a very long numeric string runs in super-linear time, a single small, well-formed TOML document containing one long integer literal can pin a Node.js process's event loop at 100% CPU for several seconds — a denial of service for any application that parses attacker-supplied or third-party TOML. No authentication or complex crafting is required. Details In `lib/parser.js`, the grammar actions that build integer nodes call `BigInt()` directly on the matched digit text, with no upper bound on its length: • `lib/parser.js:326` — hex: `BigInt('0x' + stripUnderscores(digits))` • `lib/parser.js:327` — octal: `BigInt('0o' + stripUnderscores(digits))` • `lib/parser.js:328` — binary: `BigInt('0b' + stripUnderscores(digits))` • `lib/parser.js:329` — decimal: `BigInt(stripUnderscores(text))` The parser does enforce a nesting-depth limit (`MAX_DEPTH`, default 500, `lib/parser.js:4343`) to guard against stack overflow from deeply nested arrays/inline tables (per GHSA-82x6-q7mm-w9cf). However, that guard only bounds *structural nesting* — it does not bound the length of a single scalar token. The subsequent 64-bit range check in `lib/compiler.js` (`reduceInteger`, lines 143–150, comparing against `INT64_MIN` / `INT64_MAX` defined at lines 3–4) happens after the expensive `BigInt()` conversion has already completed. It therefore provides no protection against this cost — the CPU time is already spent by the time the value is rejected as out of range. PoC ```js const toml = require('toml'); const N = 5_000_000; // ~5 MB request body const doc = 'x = 0x' + 'f'.repeat(N); const start = Date.now(); try { toml.parse(doc); // eventually throws "outside the 64-bit signed integer range" — // but only after the costly conversion has run } catch (e) {} console.log('elapsed:', Date.now() - start, 'ms'); ``` Measured results: | Digits (hex) | Approx. payload size | Parse time | |---:|---:|---:| | 200,000 | ~200 KB | 141 ms | | 400,000 | ~400 KB | 276 ms | | 800,000 | ~800 KB | 685 ms | | 1,600,000 | ~1.6 MB | 1,761 ms | | 5,000,000 | ~5 MB | 6,061 ms | Growth is clearly super-linear. The same behavior reproduces for plain decimal literals (3,000,000 `'9'` digits → ~6.3 s). Impact Any application that calls `toml.parse()` on untrusted or third-party input — config upload endpoints, CI/CD tools ingesting user-supplied `.toml` files, package managers, linters, editors/language servers — is exposed. During the conversion, the event loop is fully blocked. In a typical single-threaded Node.js server this stalls all concurrent request handling, not just the request containing the malicious payload. A single ~5 MB request is sufficient to cause several seconds of full CPU denial of service. Suggested fix: Reject digit sequences above a reasonable length *before* calling `BigInt()`, analogous to the existing `maxDepth` option. A 64-bit signed integer requires at most 20 decimal digits or 16 hex digits, so any digit sequence significantly longer than that is guaranteed to fail the existing range check anyway, and can be rejected with a cheap `.length` comparison instead of paying for the full `BigInt` conversion.