[UNIX] Lynx Format String Vulnerability in URL Logging

From: support@securiteam.com
Date: 01/04/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Fri,  4 Jan 2002 19:56:13 +0100 (CET)

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
- - promotion

When was the last time you checked your server's security?
How about a monthly report?
http://www.AutomatedScanning.com - Know that you're safe.
- - - - - - - - -

  Lynx Format String Vulnerability in URL Logging
------------------------------------------------------------------------

SUMMARY

Lynx is a popular text-mode WWW browser. The product contains a format
string vulnerability in LYUtils.c line 7995 due to a bad call to syslog(),
where the format argument is omitted. This would allow an attacker to
cause the program to execute arbitrary commands.

DETAILS

Vulnerable systems:
Lynx version 2.8.5dev.5 (FreeBSD port)
Lynx version 2.8.4rel.1

Vulnerable code:
Line 7995 in LYUtils.c reads:
syslog (LOG_INFO|LOG_LOCAL5, buf);

Exploit:
The following URL triggers the bug:
$ lynx hsVd632k@example.org/bleh:80">http://lwc%d%d:hsVd632k@example.org/bleh:80

Results in the following logged to syslog.
Dec 25 23:11:00 vapid lynx[5160]:
http://lwc-1077939384134744128:******@example.org/bleh:80

Fix:
line 7995:
- -syslog (LOG_INFO|LOG_LOCAL5, buf);
+syslog (LOG_INFO|LOG_LOCAL5,"%s", buf);

ADDITIONAL INFORMATION

The information has been provided by <mailto:lwc@vapid.dhs.org> Larry W.
Cashdollar.

========================================

This bulletin is sent to members of the SecuriTeam mailing list.
To unsubscribe from the list, send mail with an empty subject line and body to: list-unsubscribe@securiteam.com
In order to subscribe to the mailing list, simply forward this email to: list-subscribe@securiteam.com

====================
====================

DISCLAIMER:
The information in this bulletin is provided "AS IS" without warranty of any kind.
In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.

Relevant Pages