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Multiple Vendor wget/curl NTLM Username Buffer Overflow Vulnerability

10.13.05

BACKGROUND

GNU Wget is a free software package for retrieving files using HTTP,
HTTPS and FTP, the most widely-used Internet protocols. It is a
non-interactive commandline tool, so it may easily be called from
scripts, cron jobs, terminals without X-Windows support, etc. More
information on Wget is available from the vendor website:

 http://www.gnu.org/software/wget/wget.html

curl is a command line tool for transferring files with URL syntax,
supporting FTP, FTPS, HTTP, HTTPS, GOPHER, TELNET, DICT, FILE and LDAP.
Curl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading,
HTTP form based upload, proxies, cookies, user+password authentication
(Basic, Digest, NTLM, Negotiate, kerberos...), file transfer resume,
proxy tunneling and a busload of other useful tricks. More information
on curl is available from the vendor website:

 http://curl.haxx.se/

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in multiple
vendor's implementations of curl and wget allows attackers to execute
arbitrary code.

The vulnerability specifically exists due to insufficient bounds
checking on user-supplied data supplied to a memory copy operation. The
memcpy() of the supplied ntlm username to ntlmbuf shown below results
in a stack overflow:

http-ntlm.c in ntlm_output() on line 532:

    /* size is now 64 */
    size=64;
    ntlmbuf[62]=ntlmbuf[63]=0;

    memcpy(&ntlmbuf[size], domain, domlen);
    size += domlen;

    memcpy(&ntlmbuf[size], usr, userlen);
    size += userlen;

The resulting stack overflow can be leveraged to gain arbitrary code
execution with user privileges.

ANALYSIS

Successful exploitation of the vulnerability allows remote attackers to
execute arbitrary code with permissions of the http client process.
User interaction is required. Exploitation requires a user to use one
of the affected clients to connect to a malicious website.

This vulnerability affects both wget and curl clients similarly because
wget 1.10 adopted the curl ntlm authentication source code into its own
code base. The described vulnerability requires that ntlm authentication
is enabled in the affected client versions. A factor that somewhat
increases the risk of this vulnerability is that a client can be forced
to reconnect using ntlm authentication by issuing a HTTP 302 REDIRECT
command to the connecting client.

DETECTION

iDEFENSE Labs has confirmed the following software versions are
vulnerable:

       wget 1.10
       curl 7.13.2
       libcurl 7.13.2

WORKAROUND

As a workaround solution, disable NTLM support in wget and curl
installations.

VENDOR RESPONSE

wget 1.10.2 has been released to address this issue and is available for
download at:

   http://ftp.gnu.org/pub/gnu/wget/

curl has released the following patch to address this issue:

   http://curl.haxx.se/libcurl-ntlmbuf.patch

curl has also released the following security advisory:

   http://curl.haxx.se/mail/lib-2005-10/0061.html
  
Additionally, the maintainers of curl-web have provided the following
details on affected versions:

Affected versions: curl and libcurl 7.10.6 to and including 7.14.1

Not affected versions: curl and libcurl 7.10.5 and earlier,
  7.15.0 and later

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-3185 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

10/12/2005   Initial vendor notification
10/12/2005   Initial vendor response
10/13/2005   Coordinated public disclosure

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2005 Verisign, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.