Arbitrary File Write via Archive Extraction (Zip Slip) Affecting ca.uhn.hapi.fhir:org.hl7.fhir.r4b package, versions [,5.6.92)



    Attack Complexity Low
    Privileges Required High
    Confidentiality High
    Integrity High
    Availability High

    Threat Intelligence

    EPSS 0.11% (43rd percentile)
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8.1 high

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  • published 24 Jan 2023
  • disclosed 23 Jan 2023
  • credit Jonathan Leitschuh

How to fix?

Upgrade ca.uhn.hapi.fhir:org.hl7.fhir.r4b to version 5.6.92 or higher.


Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) as there are no validations that zip files being unpacked have entries that are not maliciously writing outside of the intended destination directory.


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