Researchers have discovered several vulnerabilities in the popular image processing suite ImageMagick, including a serious remote code execution flaw that has been exploited in the wild.
ImageMagick is a free and open-source software package that allows users to display, convert and edit image files. The ImageMagick library is used by many image-processing plugins, which means that the software is present in a large number of web applications.
While analyzing a flaw found by a researcher who uses the online moniker “Stewie,” Nikolay Ermishkin from the Mail.Ru security team discovered a remote code execution vulnerability (CVE-2016-3714) related to insuficient filtering of shell characters.
The vulnerability, dubbed “ImageTragick,” can be exploited by uploading a specially crafted file to a website that processes images using ImageMagick.
An attacker can create an exploit file and assign it an image extension, such as .png, in order to bypass the targeted site’s file type checks. ImageMagick determines the file type based on so-called “magic bytes,” the first few bytes of a file that are specific to each file type. Once it detects that it’s not an actual .png, ImageMagick converts the file and the malicious code is executed in the process, allowing the attacker to gain access to the targeted server.
ImageTragick: Upload(meme.png)->(IM detects non-png format based on file magic)->(IM uses insecure delegates to decode)->Shells!
— HD Moore (@hdmoore) May 3, 2016
An exploit for this vulnerability is publicly available and experts say it has already been leveraged in the wild.
ImageMagick developers attempted to patch the vulnerability with the release of versions 6.9.3-9 and 7.0.1-0 on April 30, but researchers say the fix is incomplete. Another patch will be included in ImageMagick 7.0.1-1 and 6.9.3-10, which are expected to become available by this weekend.
In the meantime, users have been advised to disable vulnerable coders by modifying their policy files. Another mitigation involves verifying that magic bytes correspond to image file types before sending the file to ImageMagick for processing.
Other vulnerabilities found in ImageMagick can be exploited to move, read or delete files (CVE-2016-3716, CVE-2016-3717 and CVE-2016-3715), and for server-side request forgery, or SSRF, attacks (CVE-2016-3718).
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