Arbitrary File Write via Archive Extraction (Zip Slip) Affecting torchserve package, versions [,0.9.0)

torchserve is a TorchServe is a tool for serving neural net models for inference

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). An attacker can upload potentially harmful archives that contain files, which can be extracted to any location on the filesystem within the process permissions. This issue could aid third-party actors in hiding harmful code in open-source/public models, which can be downloaded from the internet, and take advantage of machines running the affected software.

Mitigation: This vulnerability can be mitigated by validating the paths of files contained within a zip archive before extracting them.

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

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