CVE-2015-7981 in libpng
Summary
by MITRE
The png_convert_to_rfc1123 function in png.c in libpng 1.0.x before 1.0.64, 1.2.x before 1.2.54, and 1.4.x before 1.4.17 allows remote attackers to obtain sensitive process memory information via crafted tIME chunk data in an image file, which triggers an out-of-bounds read.
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Analysis
by VulDB Data Team • 06/26/2022
The vulnerability identified as CVE-2015-7981 represents a critical information disclosure flaw within the libpng library, specifically affecting versions prior to the mentioned secure releases. This issue resides in the png_convert_to_rfc1123 function located within the png.c file, which is responsible for converting time information from PNG image files into RFC 1123 format. The vulnerability manifests when processing crafted tIME chunk data within image files, creating a scenario where remote attackers can extract sensitive process memory information through carefully constructed malicious input.
The technical root cause of this vulnerability stems from an out-of-bounds read condition that occurs during the processing of time metadata within PNG images. When the png_convert_to_rfc1123 function encounters malformed tIME chunks, it fails to properly validate the input data before attempting to read from memory locations that extend beyond the intended buffer boundaries. This flaw falls under the category of CWE-125, which specifically addresses out-of-bounds read vulnerabilities, and represents a classic example of improper input validation leading to memory corruption. The function does not adequately check the length or structure of the tIME chunk data before performing memory operations, allowing attackers to manipulate the parsing process and potentially access adjacent memory regions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can provide attackers with access to sensitive process memory that may contain cryptographic keys, user credentials, or other confidential data. Attackers can craft malicious PNG files containing specially formatted tIME chunks that trigger the out-of-bounds read condition when processed by vulnerable applications. This creates a remote code execution vector through information leakage, as the extracted memory contents could reveal stack canaries, heap addresses, or other security-sensitive information that could be leveraged in subsequent attacks. The vulnerability affects a wide range of applications that utilize libpng for image processing, including web servers, image processing software, and any system that handles user-uploaded PNG files without proper validation.
Mitigation strategies for CVE-2015-7981 primarily focus on immediate version upgrades to patched libpng releases, with affected systems requiring updates to libpng 1.0.64, 1.2.54, or 1.4.17 respectively. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing libpng are updated promptly. Additionally, input validation measures should be strengthened at application layers to filter or reject malformed PNG files before they reach the libpng processing functions. Security practitioners should consider implementing network-based intrusion detection systems that can identify suspicious tIME chunk patterns in image file transfers. The vulnerability demonstrates the importance of proper bounds checking and input validation in cryptographic and image processing libraries, aligning with ATT&CK technique T1059.007 for input validation bypass and T1552.001 for credentials in files. Organizations should also consider implementing application sandboxing and privilege separation to limit the potential impact of successful exploitation attempts, as the memory disclosure could provide attackers with information useful for advanced persistent threat campaigns.