Vulnerability Note VU#685996

GNU Wget creates arbitrary symbolic links during recursive FTP download

Original Release date: 28 Oct 2014 | Last revised: 31 Oct 2014

Overview

GNU wget allows arbitrary filesystem access when creating symbolic links during a recursive FTP download. This allows an attacker to overwrite files with the permissions of the user running wget.

Description

CWE-59: CWE-59: Improper Link Resolution Before File Access ('Link Following')

Wget is a common Unix utility to retrieve remote files. When wget is running in recursive mode (the -m or -r switch) with a FTP server as the destination, it is vulnerable to a link following attack. A malicious FTP server, when configured to provide symlinks in the directory listing, can force the client wget utility to enter into the the specified local symlink, navigating the local file system for the attacker. Wget will then download and create or overwrite existing files within the local symlink, setting permissions to those of the remote files.

See the Rapid7 advisory for more details.

Impact

A remote unauthenticated malicious FTP server, connected to the victim via wget, can create and overwrite arbitrary files in the context of the user running wget.

Solution

Apply an Update

This vulnerability is addressed in wget 1.16. Updates should also be available in various package formats for downstream Linux distributions. Check your distribution's package management system for updates.

Enable wget symlink traversal

In wget versions 1.15 and earlier, configure retr-symlinks=on in /etc/wgetrc or ~/.wgetrc or specify --retr-symlinks as a command line option to wget.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate Updated
GNU wgetAffected-28 Oct 2014
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base 5.8 AV:N/AC:M/Au:N/C:N/I:P/A:P
Temporal 4.8 E:F/RL:OF/RC:C
Environmental 3.6 CDP:ND/TD:M/CR:ND/IR:ND/AR:ND

References

Credit

Thanks to HD Moore and John Hart of Rapid7, Inc. for reporting this vulnerability.

This document was written by Chris King.

Other Information

  • CVE IDs: CVE-2014-4877
  • Date Public: 27 Oct 2014
  • Date First Published: 28 Oct 2014
  • Date Last Updated: 31 Oct 2014
  • Document Revision: 27

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