Arbitrary File Write via Archive Extraction (Zip Slip) Affecting libarchive package, versions [,3.5.2)


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

EPSS
0.06% (28th percentile)

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  • Snyk IDSNYK-UNMANAGED-LIBARCHIVE-2989722
  • published24 Aug 2022
  • disclosed24 Aug 2022
  • creditmmatuska

Introduced: 24 Aug 2022

CVE-2021-31566  (opens in a new tab)
CWE-29  (opens in a new tab)

How to fix?

Upgrade libarchive to version 3.5.2 or higher.

Overview

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) when extracting an archive leading to changing modes, times, access control lists, and flags of a file outside the archive. An attacker may provide a malicious archive to a victim user, who would trigger this flaw when trying to extract the archive. A local attacker may use this flaw to gain more privileges in a system.

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

CVSS Scores

version 3.1