---
id: GHSA-c6fg-446q-cg94
title: >-
  adm-zip: getDataAsync() bypasses the maxOutputLength size guard enforced by
  the synchronous getData() path
summary: >-
  adm-zip: getDataAsync() bypasses the maxOutputLength size guard enforced by
  the synchronous getData() path
severity: medium
cvss: 5.3
cwe:
  - CWE-400
  - CWE-770
vendor: adm-zip
product: adm-zip
ecosystem: npm
affected:
  - adm-zip <= 0.6.0
patched:
  - adm-zip 0.6.1
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T23:10:35Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-c6fg-446q-cg94'
references:
  - url: >-
      https://github.com/cthackers/adm-zip/security/advisories/GHSA-c6fg-446q-cg94
  - url: >-
      https://github.com/cthackers/adm-zip/commit/491600683dacb6cb9fe0718a0eeb9cb5eb49afa6
  - url: 'https://github.com/cthackers/adm-zip/releases/tag/v0.6.1'
  - url: 'https://github.com/advisories/GHSA-c6fg-446q-cg94'
tags:
  - ghsa
  - npm
ingestedAt: '2026-09-29T23:52:50.542Z'
---

## Overview

### Summary
adm-zip enforces a `maxOutputLength` guard against decompression bombs on its synchronous `getData()` path, but the equivalent asynchronous `getDataAsync()` path does not enforce it — it accumulates and returns the entire decompressed output regardless of the entry's declared size. An application that checks an entry's declared size before deciding to process it, then reads the entry via `getDataAsync()` (a completely ordinary, often-recommended choice for I/O in Node.js), gets none of the protection it believes it has.


### Details

- `methods/inflater.js:3-10` passes `{maxOutputLength: expectedLength}` to `inflateRawSync`, which Node enforces.
- `methods/inflater.js:12-31` passes the same option to `createInflateRaw` but never enforces it on the streaming path — it just accumulates every chunk and allocates a final Buffer of whatever size resulted.


### PoC

```js
const AdmZip = require('adm-zip');
const zip = new AdmZip();
zip.addFile('p', Buffer.alloc(64 * 1024 * 1024, 0x41)); // 64 MiB
const raw = Buffer.from(zip.toBuffer());
// patch the local + central declared uncompressed size to 1 byte
raw.writeUInt32LE(1, localHeaderSizeOffset);
raw.writeUInt32LE(1, centralHeaderSizeOffset);
const entry = new AdmZip(raw).getEntry('p');

entry.getData();
// throws: ERR_BUFFER_TOO_LARGE: Cannot create a Buffer larger than 1 bytes

entry.getDataAsync((data, error) => { ... });
// returns the full 67,108,864-byte buffer, error is undefined
```

### Impact
An application that validates a declared size before reading an entry, then uses the async API, gets no protection against a high-ratio DEFLATE payload. Repeated or larger requests could contribute to memory exhaustion.

## Affected packages

- `adm-zip <= 0.6.0`

## Remediation

Upgrade to a patched release:

- `adm-zip 0.6.1`