music-metadata is a metadata parser for audio and video media files. Prior to 11.16.0, the Matroska and WebM EBML parser decodes an attacker-controlled VINT element length and uses it for string-token or Uint8Array allocation before confirming that the leaf fits within its parent or available input. Crafted WebM, MKV, or MKA inputs can cause disproportionate allocations, out-of-memory denial of service, or, for a demonstrated parseFile path on Node.js 26.7.0, an uncatchable V8 fatal abort. The exact failure mode depends on the tokenizer, parser API, and runtime, but the affected leaf-length validation flaw is shared and has availability impact only. This issue is fixed in version 11.16.0.

Affected: npm: music-metadata

## Summary

The Matroska/WebM EBML parser decodes attacker-controlled variable-length integer (VINT) element lengths without first validating that the declared element fits within its enclosing container or the available input. Leaf lengths are then used directly for string-token and `Uint8Array` allocations.

A very small crafted `.webm`, `.mkv`, or `.mka` file can therefore cause a disproportionately large allocation, an out-of-memory denial of service, or—in one demonstrated `parseFile` case—an uncatchable V8 fatal abort.

## Impact

Applications that parse untrusted Matroska/WebM media can be denied service. Depending on the input, parser API, and Node.js/V8 version, the demonstrated outcomes include:

- a 34-byte input causing an approximately 128 MiB allocation before end-of-input; - a 70-byte input causing a 500 MiB allocation through a binary EBML leaf, with concurrent parses multiplying memory consumption; - a 48-byte file causing an uncatchable V8 fatal abort through `parseFile` when a leaf declares a length of 32 GiB.

The fatal-abort case was reproduced on `music-metadata` 11.15.0 with Node.js 26.7.0. It was deterministic across three runs and exited with code 133 despite a surrounding `try`/`catch`. The same reporter did not reproduce that fatal abort through `parseBuffer` on Node.js 20 through 25; those configurations can still encounter allocation attempts or catchable errors. The exact failure mode is therefore runtime- and tokenizer-dependent, but the underl…