The Common UNIX Printing System, more commonly referred to as CUPS, provides a standard printer interface for various Unix based operating systems. "imagetops" is a part of CUPS responsible for creating PostScript representations of different graphic file formats. For more information, visit the vendor's website at the following URL.
Remote exploitation of a heap-based buffer overflow vulnerability in CUPS, as included in various vendors' operating system distributions, could allow an attacker to execute arbitrary code with the privileges of the affected service.
The Common Unix Printing System, more commonly referred to as CUPS, provides a standard printer interface for various Unix-based operating systems.
The Silicon Graphics Image (SGI) file format parsing module is vulnerable to a heap-based buffer overflow vulnerability when parsing malformed Run Length Encoded (RLE) data. The vulnerability exists within the read_rle16() function. This function doesn't correctly validate the row count value taken from the file, which is then used to control how many 16-bit integers to store into a heap-based buffer. By providing small image dimensions and a large row count, it is possible to trigger a heap-based buffer overflow.
Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the affected service. Depending on the underlying operating system and distribution, CUPS may run as the lp, daemon or a different user.
Exploiting heap overflow vulnerabilities on modern Unix systems can be difficult due to various heap protection schemes; however, the attacker has very fine-grained control over the overflow, which somewhat eases the difficulty of exploitation.
To exploit this vulnerability remotely, the targeted host must be sharing a printer(s) on the network. If a printer is not being shared, CUPS only listens on the localhost interface, and the scope of this vulnerability would be limited to local privilege escalation.
iDefense has confirmed the existence of this vulnerability in CUPS version 1.3.7. Previous versions may also be affected.
Disabling printer sharing will prevent this vulnerability from being exploited remotely; however, local exploitation is still possible.
CUPS.org has released a patch which addresses this issue. For more information, consult their advisory at the following URL.
A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet.
09/02/2008 Initial Vendor Notification
10/09/2008 Public Disclosure
This vulnerability was reported to iDefense by regenrecht.
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