CVE-2011-2690 in libpng
Summary
by MITRE
Buffer overflow in libpng 1.0.x before 1.0.55, 1.2.x before 1.2.45, 1.4.x before 1.4.8, and 1.5.x before 1.5.4, when used by an application that calls the png_rgb_to_gray function but not the png_set_expand function, allows remote attackers to overwrite memory with an arbitrary amount of data, and possibly have unspecified other impact, via a crafted PNG image.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2690 represents a critical buffer overflow flaw within the libpng library ecosystem that has persisted across multiple version branches including 1.0.x, 1.2.x, 1.4.x, and 1.5.x. This vulnerability specifically targets applications that utilize the png_rgb_to_gray function without properly implementing the png_set_expand function, creating a dangerous condition where maliciously crafted PNG images can trigger memory corruption. The flaw stems from inadequate bounds checking during the processing of RGB color values when converting them to grayscale, allowing attackers to inject arbitrary data beyond allocated memory buffers. This vulnerability falls under the CWE-121 category of stack-based buffer overflow, which is classified as a fundamental memory safety issue that has been a persistent concern in software development practices since the early days of computing.
The technical exploitation of this vulnerability occurs when an application processes a specially crafted PNG image that contains malformed color data. During the conversion process from RGB to grayscale, the libpng library fails to validate the size of incoming color values against the expected buffer dimensions, enabling attackers to overwrite adjacent memory locations with controlled data patterns. This memory corruption can potentially lead to arbitrary code execution, application crashes, or other unspecified behaviors that may be leveraged for more sophisticated attacks. The vulnerability's impact is particularly severe because it can be triggered through standard image processing workflows that are common in web applications, image viewers, and content management systems, making it a prime target for remote exploitation scenarios. The specific function call sequence that triggers this vulnerability requires the png_rgb_to_gray function to be invoked without the protective png_set_expand function, which acts as a safeguard mechanism that properly handles color expansion and validation.
From an operational standpoint, this vulnerability presents significant risk to organizations that rely on libpng for image processing capabilities, particularly in web environments where user-uploaded images are common. The vulnerability affects not only web applications but also desktop software, mobile applications, and server-side image processing systems that utilize the affected library versions. Attackers can exploit this flaw by uploading or delivering malicious PNG files that, when processed by vulnerable applications, will trigger the buffer overflow condition. The implications extend beyond simple denial of service to potential privilege escalation and system compromise, as demonstrated by various real-world exploitation techniques that have been documented in security research. This vulnerability has been classified under the attack technique T1059 in the MITRE ATT&CK framework, specifically related to command and scripting interpreter execution, as the memory corruption can lead to code execution opportunities that attackers can leverage for further system compromise.
Organizations should prioritize immediate remediation by upgrading to libpng versions that have addressed this vulnerability, specifically versions 1.0.55, 1.2.45, 1.4.8, and 1.5.4 or later. The recommended mitigation strategy involves not only patching the library but also implementing proper input validation and sanitization measures at the application level. Security teams should conduct comprehensive vulnerability assessments to identify all applications that utilize affected libpng versions and ensure that proper error handling is implemented to prevent exploitation attempts. Additionally, implementing network-based intrusion detection systems that can identify and block suspicious PNG file patterns can provide an additional layer of protection. The vulnerability demonstrates the critical importance of maintaining up-to-date third-party libraries and implementing comprehensive software supply chain security practices, as this flaw had remained unpatched for an extended period and affected numerous applications across different platforms and operating systems.