CVE-2015-2158 in pngcrush
Summary
by MITRE
Off-by-one error in the pngcrush_measure_idat function in pngcrush.c in pngcrush before 1.7.84 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted PNG file.
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Analysis
by VulDB Data Team • 11/22/2019
The vulnerability identified as CVE-2015-2158 represents a critical off-by-one error within the pngcrush image processing utility, specifically within the pngcrush_measure_idat function located in the pngcrush.c source file. This flaw exists in versions prior to 1.7.84 and demonstrates a classic buffer overflow condition that can be exploited through maliciously crafted PNG image files. The vulnerability stems from improper boundary checking during the processing of PNG image data streams, particularly when handling the IDAT chunk which contains the actual image data. When an attacker submits a specially crafted PNG file, the application fails to properly validate the size parameters of the IDAT chunk, leading to memory corruption that manifests as application instability.
The technical implementation of this vulnerability involves the pngcrush_measure_idat function failing to correctly calculate or validate the boundaries of image data segments during PNG file parsing. This off-by-one error creates a scenario where memory access occurs beyond the allocated buffer boundaries, potentially allowing attackers to manipulate memory layout and execution flow. The flaw operates at the intersection of memory safety and image processing, where legitimate image parsing logic encounters malformed input that triggers undefined behavior. The vulnerability can be classified under CWE-129 as an "Improper Validation of Array Index" and also relates to CWE-125 as "Out-of-bounds Read" and CWE-787 as "Out-of-bounds Write." The specific nature of the vulnerability aligns with ATT&CK technique T1203 "Exploitation for Client Execution" as it leverages application parsing of image files to achieve remote code execution or denial of service.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable remote code execution on systems running vulnerable versions of pngcrush. When exploited, the vulnerability can cause applications using pngcrush to crash unexpectedly, leading to service disruption and potential system instability. In more severe cases, the memory corruption resulting from the off-by-one error could be manipulated to execute arbitrary code, potentially allowing attackers to gain unauthorized access to affected systems. The vulnerability affects any system or application that utilizes pngcrush for PNG file processing, including web applications, image processing pipelines, and automated systems that handle user-uploaded image content. The remote exploitation capability makes this particularly dangerous in web environments where users can upload PNG files, as it enables attackers to craft malicious images that trigger the vulnerability without requiring local system access or user interaction beyond file upload.
Mitigation strategies for CVE-2015-2158 primarily focus on immediate version updates to pngcrush 1.7.84 or later, which contain the necessary fixes for the off-by-one error. System administrators should implement comprehensive patch management processes to ensure all vulnerable installations are updated promptly. Additional defensive measures include implementing strict input validation for PNG files, particularly when processing user-uploaded content, and employing sandboxing techniques to isolate image processing operations. Network-level protections can involve implementing file type validation and content inspection to prevent malicious PNG files from reaching systems that utilize pngcrush. Organizations should also consider deploying intrusion detection systems that can identify exploitation attempts targeting this specific vulnerability. The fix implemented in the updated version addresses the root cause by properly validating array indices and ensuring boundary checks are performed before memory access operations occur, thereby preventing the out-of-bounds memory access that led to the vulnerability. Security monitoring should include detection of unusual application crashes or memory access patterns that might indicate exploitation attempts, particularly in environments where PNG file processing is common.