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.
Attack Requirements
Present
AT
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
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 chmlib CHM File Handling Buffer Overflow Vulnerability
iDefense Security Advisory 10.28.05
www.idefense.com/application/poi/display?id=332&type=vulnerabilities
October 28, 2005
I. BACKGROUND
chmlib is a library for dealing with Microsoft ITSS/CHM format files.
II. DESCRIPTION
Remote exploitation of a stack overflow vulnerability in chmlib as
included in various Linux distributions allows attackers to execute
arbitrary code.
The vulnerability specifically exists due to an unchecked memory copy
while processing a CHM file. The vulnerability exists in the following
code, which is found in chm_lib.c:
static UChar *_chm_find_in_PMGL(UChar *page_buf,
UInt32
block_len,
const
char *objPath)
{
[...]
char buffer[CHM_MAX_PATHLEN+1];
/* figure out where to start and end */
cur = page_buf;
hremain = _CHM_PMGL_LEN;
if (! _unmarshal_pmgl_header(&cur, &hremain, &header))
return NULL;
end = page_buf + block_len - (header.free_space);
/* now, scan progressively */
while (cur < end)
{
/* grab the name */
temp = cur;
strLen = _chm_parse_cword(&cur);
if (! _chm_parse_UTF8(&cur, strLen, buffer))
return NULL;
[..]
_chm_parse_cword can be forced to return a value larger than
CHM_MAX_PATHLEN. This value is then used while copying user controlled
data into a CHM_MAX_PATHLEN sized stack buffer. This allows the attacker
full control over execution flow by overwriting the saved return address
on the stack.
III. ANALYSIS
Exploitation could allow attackers to execute arbitrary code with the
privileges of the user processing the CHM file. Remote exploitation can
be achieved by sending a malicious file in an e-mail message to the
target user.
IV. DETECTION
iDefense has confirmed the existence of this vulnerability in chmlib
0.35. It is suspected that all versions of chmlib are vulnerable.
The following vendors distribute susceptible chmlib packages within
their respective operating system distributions:
FreeBSD Project:
FreeBSD 5.4 and prior
Gentoo Foundation Inc.:
Gentoo Linux 1.1a, 1.2, 1.4, 2004.0, 2004.1 and 2004.2
V. WORKAROUND
Do not open CHM files sent from an untrusted source.
VI. VENDOR RESPONSE
chmlib-0.36 addresses this vulnerability and is available for download
at:
http://freshmeat.net/projects/chmlib/
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-2930 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
09/08/2005 Initial vendor notification
09/09/2005 Initial vendor response
10/28/2005 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.
This information is provided for TESTING and LEGAL RESEARCH purposes only. All trademarks used are properties of their respective owners. By visiting this website you agree to Terms of Use and Privacy Policy and Impressum