Ghostscript, an open-source implementation of Adobe’s PostScript and PDF file format, has recently addressed a bug, CVE-2023-36664, that allowed malicious documents to exploit the software. Ghostscript is widely used in various applications, including graphics programs like Inkscape. The bug stemmed from Ghostscript’s handling of output filenames, which made it possible to send data into a pipe instead of a regular file. Pipes are system objects that enable data transfer between programs without saving it to disk.
By leveraging this feature, attackers could execute system commands through the Ghostscript rendering engine. The latest version of Ghostscript, 10.01.2, resolves this vulnerability.
The use of pipes in Ghostscript’s handling of filenames introduced a potential security loophole. Traditionally, pipes facilitate communication between processes by simulating file operations while using memory instead of disk storage. This feature eliminates the need to save intermediate data to temporary files, improving efficiency.
However, it also opened the door for attackers to manipulate the system by tricking Ghostscript into running unauthorized commands. By exploiting specially-formatted filenames starting with %pipe% or |, malicious actors could execute arbitrary commands on a victim’s computer.
Addressing this bug required multiple patches, highlighting the complexity of vulnerability remediation. Initially, the Ghostscript team added a check to detect filenames starting with %pipe… However, they later realized that the code should also account for filenames starting with a pipe character (|). The updated code now deems filenames unsafe if they begin with either %pipe… or |. This revision ensures that potential security risks are mitigated.
To protect against this vulnerability, users should ensure they have the latest version of Ghostscript installed. If Ghostscript is bundled with other software, it is advisable to check with the provider for details on upgrading the Ghostscript component.
For programmers, it is crucial to go beyond immediate bug fixes and consider the possibility of similar coding mistakes and other potential exploit techniques. Thorough testing and analysis can help identify and address vulnerabilities effectively.
