A vulnerability in the Python programming language that has been overlooked for 15 years is now back in the spotlight as it likely affects more than 350,000 open-source repositories and can lead to code execution.

Trellix Advanced Research Center stumbled across a vulnerability in Python’s tarfile module. As we dug into the issue, we realized this was in fact CVE-2007-4559. The vulnerability is a path traversal attack in the extract and extractall functions in the tarfile module that allow an attacker to overwrite arbitrary files by adding the “..” sequence to filenames in a TAR archive. Over the course of our research into the impact of this vulnerability we discovered that hundreds of thousands of repositories were vulnerable to this vulnerability. While the vulnerability was originally only marked as a 6.8, we were able to confirm that in most cases an attacker can gain code execution from the file write.