The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
Low
PR
The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
S
An exploited vulnerability can affect resources beyond the security scope managed by the security authority that is managing the vulnerable component. This is often referred to as a 'privilege escalation,' where the attacker can use the exploited vulnerability to gain control of resources that were not intended or authorized.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Multiple Vendor wget/curl NTLM Username Buffer Overflow Vulnerability
iDEFENSE Security Advisory 10.13.05
www.idefense.com/application/poi/display?id=322&type=vulnerabilities
October 13, 2005
I. 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/
II. 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.
III. 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.
IV. DETECTION
iDEFENSE Labs has confirmed the following software versions are
vulnerable:
* wget 1.10
* curl 7.13.2
* libcurl 7.13.2
V. WORKAROUND
As a workaround solution, disable NTLM support in wget and curl
installations.
VI. 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
VII. 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.
VIII. DISCLOSURE TIMELINE
10/12/2005 Initial vendor notification
10/12/2005 Initial vendor response
10/13/2005 Coordinated public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp
Free tools, research and upcoming events
http://labs.idefense.com
X. LEGAL NOTICES
Copyright (c) 2005 iDEFENSE, 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 (at) idefense (dot) com [email concealed] 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.
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