Arbitrary File Write via Archive Extraction (Zip Slip) Affecting elfinder.netcore package, versions [0,]
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Test your applications- Snyk ID SNYK-DOTNET-ELFINDERNETCORE-1567778
- published 20 Aug 2021
- disclosed 20 Aug 2021
- credit Timo Müller
Introduced: 20 Aug 2021
CVE-2021-23427 Open this link in a new tabHow to fix?
There is no fixed version for elFinder.NetCore.
Overview
elFinder.NetCore is a file manager for Web.
Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). The ExtractAsync function within the FileSystem is vulnerable to arbitrary extraction due to insufficient validation.
PoC
* Upload the genearted evil.zip to the server
* extract the evil.zip file in elfinder
* You now should fine a file in the /tmp/ directory
Details
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