adm-zip: getDataAsync() bypasses the maxOutputLength size guard enforced by the synchronous getData() path
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
- Denial of service
- Confidentiality · integrity · availability
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- Fix status
- Fixed
No CVSS vector from any source. Fix status from GitHub. Impact type from CWE-400.
Summary
### 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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | adm-zip (npm) | before 0.6.1 | 0.6.1 | Patch available | GHSA-c6fg-446q-cg94 |
- adm-zip (npm) Vendor— Affected before 0.6.1 Fixed in 0.6.1 Patch available GHSA-c6fg-446q-cg94
Remediation
- Fix · GHSA-c6fg-446q-cg94 adm-zip (npm) Fixed in 0.6.1 Advisory →
Timeline
- 2026-10-03 Threatist record created from GHSA-c6fg-446q-cg94
References
Sources
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