CVE-2026-113664

### Summary The tar-extraction guard added to `@apostrophecms/import-export` for GHSA-mwxc-m426-3f78 is a literal substring test for `../`, and `./..` does not contain that substring. An entry named `./..` therefore passes the guard, `path.join` normalizes it to the parent of the export directory, and the resulting `fs.WriteStream` opens a directory and emits `EISDIR` with no `error` listener attached, which terminates the Node process. Confirmed on default-branch HEAD `1bd5d0a7a6fe880836fa75adad6964f1c577d640`, package version `3.6.2`. ### Details `packages/import-export/lib/formats/gzip.js`, in the tar-stream `entry` handler inside `extract(filepath, exportPath)`: ```js const name = header.name.replace(/\\/g, '/'); if (name.includes('../')) { // skipped } ... stream.pipe(fs.WriteStream(path.join(exportPath, name))); ``` Two separate problems sit in those four lines. The guard tests the raw entry name for a substring instead of resolving the joined path and requiring containment, and the write stream has no `error` handler, so any stream error becomes an unhandled `'error'` event. Reaching it needs an account that can import, nothing more. `packages/import-export/modules/@apostrophecms/import-export-page/index.js` exposes `post.importExportImport`, which calls into `lib/methods/import.js`; that handler requires `req.user` and then calls `format.input(exportPath)`, which for a `.gz` upload is `gzip.js` calling `extract()` on the uploaded archive. ### PoC This is not an end-to-end exploit. What follows is each of the three primitives the crash depends on, executed individually, plus a source-level trace of the route. The chain from `post.importExportImport` to `extract()` was read, not observed. The guard misses the payload: ```bash node -e "console.log('./..'.includes('../')); console.log('..'.includes('../')); console.log('a/./..'.includes('../'));" ``` ```text false false false ``` `path.join` then resolves it out of the export directory: ```bash node -e "const path=require('path'); const exportPath='/tmp/exportRoot'; console.log(path.join(exportPath,'./..'));" ``` ```text /tmp ``` And a write stream opened on a directory, with no `error` listener, kills the process rather than failing the request: ```bash node -e "const fs=require('fs'); const s=fs.createWriteStream('/tmp'); s.write('x'); s.end(); setTimeout(()=>console.log('still alive'),500);" ``` ```text events.js:291 throw er; // Unhandled 'error' event ^ Error: EISDIR: illegal operation on a directory, open '/tmp' Emitted 'error' event on WriteStream instance at: at internal/fs/streams.js:361:12 at FSReqCallback.oncomplete (fs.js:156:23) { errno: -21, code: 'EISDIR', syscall: 'open', path: '/tmp' } ``` The `events.js:291` frame shows that transcript came off the Node 14 line my audit box had. The unhandled-`error`-event behavior is not version specific, but the exact message on your supported Node versions is worth a re-run. Source-side confirmation without running anything: ```bash grep -n "includes('../')" packages/import-export/lib/formats/gzip.js grep -n "WriteStream" packages/import-export/lib/formats/gzip.js ``` ### Impact An authenticated user who can reach the import UI uploads one crafted archive and takes down the Node process handling it. Every worker that picks up such an archive dies the same way. ### Suggested fix Resolve the target and require containment, and attach an error handler: ```js const base = path.resolve(exportPath); const target = path.resolve(path.join(exportPath, name)); if (target !== base && !target.startsWith(base + path.sep)) { stream.on('end', next); stream.resume(); return; } if (header.type === 'directory') { fsp.mkdir(target).then(next).catch(reject); } else { const out = fs.WriteStream(target); out.on('error', reject); stream.pipe(out); stream.on('end', next); } ``` The error handler earns its place independently. Any tar entry that lands on an existing directory name has the same effect whether or not traversal is involved. ### Why this is not GHSA-mwxc-m426-3f78 The `name.includes('../')` check is the mitigation shipped for GHSA-mwxc-m426-3f78 / CVE-2026-32731. It stops names carrying the literal `../` sequence. It does not canonicalize the joined path, so `./..` and a bare `..` still get through, and it did not touch the missing `error` listener. This report is about what the substring test leaves behind. AI assistance was used for the code audit and drafting. The exact guard and `WriteStream` lines in `packages/import-export/lib/formats/gzip.js` at the stated HEAD were manually verified, the import route from the page module through `lib/methods/import.js` into the entry handler were manually traced, and the three Node one-liners were manually ran and copied verbatim.