Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/artdarek/go-unzip package, versions <2.0.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-GOLANG-GITHUBCOMARTDAREKGOUNZIP-3121098
- published16 Nov 2022
- disclosed14 Apr 2021
- creditSam Sanoop - Snyk Research Team
Introduced: 14 Apr 2021
CVE-2020-36560 (opens in a new tab)How to fix?
Upgrade github.com/artdarek/go-unzip to version 2.0.0 or higher.
Overview
github.com/artdarek/go-unzip is a package go-unzip provides a very simple library to extract zip archive
Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) due to improper path sanitization, so archives containing relative file paths can cause files to be written (or overwritten) outside of the target directory.
PoC
package main
import (
"./go-unzip"
"fmt"
)
/ zip file can be taken from here: https://github.com/snyk/zip-slip-vulnerability/tree/master/archives
func main() {
uz := unzip.New("/home/snoopy/ziptest/poc/ziptest2.zip", "/home/snoopy/zipper/uploads")
err := uz.Extract()
if err != nil {
fmt.Println(err)
}
}
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