CVE-2011-3170 in CUPS
Summary
by MITRE
The gif_read_lzw function in filter/image-gif.c in CUPS 1.4.8 and earlier does not properly handle the first code word in an LZW stream, which allows remote attackers to trigger a heap-based buffer overflow, and possibly execute arbitrary code, via a crafted stream, a different vulnerability than CVE-2011-2896.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability identified as CVE-2011-3170 affects the CUPS (Common Unix Printing System) version 1.4.8 and earlier, specifically within the gif_read_lzw function located in the filter/image-gif.c file. This issue represents a heap-based buffer overflow that occurs during the processing of GIF image files through the CUPS printing system. The flaw arises from improper handling of the initial code word within an LZW (Lempel-Ziv-Welch) compression stream, which is fundamental to GIF image format processing. When a maliciously crafted GIF file is processed by CUPS, the system fails to properly validate or handle the first code word, leading to memory corruption that can be exploited remotely.
The technical implementation of this vulnerability stems from the LZW decompression algorithm's handling of the initial code word sequence. In standard LZW decompression, the first code word typically represents a special marker or initial dictionary entry that establishes the compression context. The gif_read_lzw function in CUPS fails to properly validate this critical initial value, allowing an attacker to manipulate the decompression process. This mismanagement results in a buffer overflow condition where data is written beyond the allocated heap memory boundaries. The vulnerability is particularly concerning because it operates within a print filter context, meaning that any application or user that processes GIF images through CUPS could be vulnerable to remote exploitation.
The operational impact of CVE-2011-3170 extends beyond simple denial-of-service conditions to potentially enable arbitrary code execution on affected systems. This represents a significant security risk for networked printing environments where CUPS serves as a central printing service. Attackers can craft malicious GIF files that, when processed by CUPS, cause the heap overflow to occur during image rendering or printing operations. The vulnerability's remote exploitation capability means that attackers do not need physical access to the system, as the attack can be delivered through network-based printing services or web interfaces that utilize CUPS for image processing. Systems running vulnerable versions of CUPS are at risk of being compromised, potentially allowing attackers to execute malicious code with the privileges of the CUPS service account, which typically runs with elevated system permissions.
This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates characteristics consistent with the ATT&CK technique T1059.007 for command and scripting interpreter. The exploitation pattern follows typical remote code execution vectors where input validation failures lead to memory corruption. Organizations using CUPS for printing services should prioritize patching their systems, as the vulnerability affects a core component of many printing infrastructures. The fix involves implementing proper validation of the initial code word in the LZW stream processing, ensuring that the decompression algorithm correctly handles boundary conditions and prevents memory corruption. Additionally, network segmentation and access controls should be implemented to limit exposure of CUPS services to untrusted networks, reducing the attack surface for potential exploitation of this and related vulnerabilities.