Public Vulnerability Reports

libtiff STRIPOFFSETS Integer Overflow Vulnerability

12.21.04

BACKGROUND

libtiff provides support for the Tag Image File Format (TIFF), a widely
used format for storing image data.

More information is available at the following site:
http://www.remotesensing.org/libtiff/

DESCRIPTION

Remote exploitation of an integer overflow in libtiff may allow for the
execution of arbitrary code.

The overflow occurs in the parsing of TIFF files set with the
STRIPOFFSETS flag in libtiff/tif_dirread.c. In the TIFFFetchStripThing()
function, the number of strips (nstrips) is used directly in a
CheckMalloc() routine without sanity checking. The call ultimately boils
down to:

malloc(user_supplied_int*size(int32));

When supplied 0x40000000 as the user supplied integer, malloc is called
with a length argument of 0. This has the effect of returning the
smallest possible malloc chunk. A user controlled buffer is subsequently
copied to that small heap buffer, causing a heap overflow.

When exploited, it is possible to overwrite heap structures and seize
control of execution.

ANALYSIS

An attacker can exploit the above-described vulnerability to execute
arbitrary code under the permissions of the target user. Successful
exploitation requires that the attacker convince the end user to open
the malicious TIFF file using an application linked with a vulnerable
version of libtiff. Exploitation of this vulnerability against a remote
target is difficult because of the precision required in the attack.

DETECTION

iDEFENSE has confirmed this vulnerability in libtiff 3.6.1. Changes were
introduced in libtiff 3.7.0 that had the effect of fixing this
vulnerability.

The following vendors provide susceptible libtiff packages within their
respective operating system distributions:
 
 - Gentoo Linux
 - Fedora Core
 - Red Hat Linux
 - SuSE Linux
 - Debian Linux

WORKAROUND

Only open TIFF files from trusted users.

VENDOR RESPONSE

This issue is addressed in libtiff 3.7.0 and 3.7.1.

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2004-1307 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

12/15/2004   Discovery of fix in later software version
12/21/2004   Public disclosure

CREDIT

infamous41md[at]hotpop.com is credited with this discovery.

Get paid for vulnerability research
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LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

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at the time of publishing based on currently available information. Use
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