Critical flaws in ImageMagick library expose websites to hacking

The vulnerabilities were discovered by Nikolay Ermishkin from the Mail.Ru security team and were reported to the ImageMagick developers who attempted a fix in version 6.9.3-9, released on April 30. However, the fix is incomplete and the vulnerabilities can still be exploited.

Furthermore, there is evidence that people aside from security researchers and  ImageMagick developers know about the flaws, which is why their existence was publicly disclosed Tuesday. The flaws can be exploited by uploading specially crafted images to Web applications that rely on ImageMagick to process them.

ImageMagick is a command-line tool that can be used to create, edit and convert a large number of image file formats. Its library is the base for other Web server packages like PHP’s imagick, Ruby’s rmagick and papercli and Node.js’s imagemagick.

Since the public disclosure Tuesday, security researchers have already developed proof-of-concept exploits for the issues. This means that attackers could too, increasing the likelihood of malicious in-the-wild attacks.

Security researchers have dubbed the set of flaws ImageTragick and created a website with more information for website developers and administrators, including mitigation advice until a complete patch is made available.

"Verify that all image files begin with the expected 'magic bytes' corresponding to the image file types you support before sending them to ImageMagick for processing," the researchers said on the website. "Use a policy file to disable the vulnerable ImageMagick coders. The global policy for ImageMagick is usually found in '/etc/ImageMagick'."

The ImageMagick developers have also suggested the policy-based mitigation and posted an example policy file on their support forum.