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 UpdatedGNU wgetAffected-28 Oct 2014If 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

http://git.savannah.gnu.org/cgit/wget.git/commit/?id=18b0979357ed7dc4e11d4f2b1d7e0f5932d82aa7
http://cwe.mitre.org/data/definitions/59.html
https://bugzilla.redhat.com/show_bug.cgi?id=1139181
https://community.rapid7.com/community/metasploit/blog/2014/10/28/r7-2014-15-gnu-wget-ftp-symlink-arbitrary-filesystem-access
http://www.gnu.org/software/wget/manual/wget.html#index-symbolic-links_002c-retrieving
http://gnu.huihoo.org/wget-1.8.1/html_node/wget_10.html
http://comments.gmane.org/gmane.comp.web.wget.general/10367

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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