Find, fix and prevent vulnerabilities in your code.

Overview

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

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) due to improper sanitization of filenames when files are loaded with the loadAsync method.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade jszip to version 2.7.0, 3.8.0 or higher.

References

• Changelog
• GitHub Commit

Overview

d3-color is a Color spaces! RGB, HSL, Cubehelix, Lab and HCL (Lch).

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the rgb() and hrc() functions.

PoC by Yeting Li:

var d3Color = require("d3-color")
// d3Color.rgb("rgb(255,255,255)")

function build_blank(n) {
    var ret = "rgb("
    for (var i = 0; i < n; i++) {
        ret += "1"
    }
    return ret + "!";
}

for(var i = 1; i <= 5000000; i++) {
    if (i % 1000 == 0) {
        var time = Date.now();
        var attack_str = build_blank(i)
        d3Color.rgb(attack_str)
        var time_cost = Date.now() - time;
        console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
    }
}

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

• A The string must start with the letter 'A'
• (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
• D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

1. CCC
2. CC+C
3. C+CC
4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade d3-color to version 3.1.0 or higher.

References

• Github PR
• Github PR
• GitHub PR
• Github Releases

Overview

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();

Details

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

Remediation

Upgrade jszip to version 3.7.0 or higher.

References

• GitHub Commit
• GitHub Issue
• GitHub PR