The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
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
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
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
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
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 xpdf StreamPredictor Heap Overflow Vulnerability
iDefense Security Advisory 12.05.05
www.idefense.com/application/poi/display?id=344&type=vulnerabilities
December 5, 2005
I. BACKGROUND
Xpdf is an open-source viewer for Portable Document Format (PDF) files.
II. DESCRIPTION
Local exploitation of a heap-based buffer overflow vulnerability in
xpdf, as included by various vendor's software distributions, could
allow attackers to cause a denial of service (DoS) condition,
potentially resulting in arbitrary code execution.
The vulnerability specifically exists due to insufficient input
validation in the Predictor stream parsing code. The
StreamPredictor::StreamPredictor function from xpdf/Stream.cc takes the
value of numComps from user-controllable data from within the PDF file.
The numComps value is used in a series of calcualations within the
StreamPredictor function. Using specially crafted values, a call to
gmalloc can be forced to allocate the minimum number of bytes, which
may later be overrun with user-supplied data from the PDF file leading
to corruption of heap memory that might result in a DoS condition or
arbitrary code execution.
III. ANALYSIS
Exploitation could result in arbitrary code execution with privileges
of the xpdf process. Currently, exploitation resulting in code
execution is theoretical and dependant on the process memory layout. A
typical exploitation attempt would require an attacker to supply a
malicious pdf to the victim. The victim would need to open the corrupt
pdf file in xpdf. Only then would the vulnerability be triggered.
IV. DETECTION
iDefense has confirmed the existence of this vulnerability in xpdf
3.01. All earlier versions of xpdf are suspected vulnerable.
The following vendors include susceptible xpdf packages within their
operating system distributions:
. The Debian Project: Linux 3.0 and 3.1
V. WORKAROUND
iDefense is currently unaware of any effective workarounds for this
vulnerability.
VI. VENDOR RESPONSE
A patch for this vulnerability is available at:
ftp://ftp.foolabs.com/pub/xpdf/xpdf-3.01pl1.patch
Updated binaries (version 3.01pl1) are available at:
http://www.foolabs.com/xpdf/download.html
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-3192 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
10/13/2005 Initial vendor notification
10/19/2005 Initial vendor response
12/05/2005 Coordinated public disclosure
IX. CREDIT
iDefense credits infamous41md (at) hotpop (dot) com [email concealed] with the discovery of this
vulnerability.
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X. LEGAL NOTICES
Copyright C 2005 iDefense, Inc.
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part of this alert in any other medium other than electronically, please
email customerservice (at) iDefense (dot) com [email concealed] for permission.
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