CVE-2016-3982 in OptiPNG
Summary
by MITRE
Off-by-one error in the bmp_rle4_fread function in pngxrbmp.c in OptiPNG before 0.7.6 allows remote attackers to cause a denial of service (out-of-bounds read or write access and crash) or possibly execute arbitrary code via a crafted image file, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability identified as CVE-2016-3982 represents a critical off-by-one error within the bmp_rle4_fread function located in the pngxrbmp.c file of OptiPNG software versions prior to 0.7.6. This flaw constitutes a classic buffer overflow condition that arises from improper bounds checking during the processing of bitmap image files with RLE4 compression. The issue manifests when the application attempts to read or write data beyond the allocated memory boundaries, creating a scenario where maliciously crafted image files can trigger unpredictable behavior in the affected software.
The technical implementation of this vulnerability stems from insufficient input validation and boundary checking mechanisms within the image parsing logic. When OptiPNG processes a specially crafted bitmap file containing RLE4 encoded data, the bmp_rle4_fread function fails to properly verify array indices against the actual buffer dimensions. This off-by-one error creates a condition where the program may attempt to access memory locations that are either uninitialized or belong to other data structures, leading to memory corruption that can result in either out-of-bounds read operations or heap-based buffer overflows. The vulnerability's classification as heap-based indicates that the corrupted memory regions are allocated on the heap, making the exploitation more complex but potentially more dangerous due to the controlled nature of heap memory layout.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous for systems that process untrusted image files. Attackers can leverage this flaw by crafting malicious bitmap files that, when processed by vulnerable OptiPNG versions, will cause the application to crash or potentially execute arbitrary code with the privileges of the user running the software. This presents significant risk in automated image processing pipelines, web applications that accept image uploads, and systems where OptiPNG is used for batch image optimization. The vulnerability affects the core functionality of image processing and can be exploited in contexts where users or applications are unaware of the malicious nature of the input files.
Mitigation strategies for this vulnerability include immediate upgrade to OptiPNG version 0.7.6 or later, which contains the necessary patches to address the boundary checking issues in the bmp_rle4_fread function. System administrators should also implement input validation measures that sanitize image file inputs before processing, including file format verification and size limitations. Additionally, deploying application sandboxing techniques and restricting file processing permissions can help contain potential exploitation attempts. The vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a variant of the broader class of buffer overflow vulnerabilities that are frequently targeted in exploit development. Organizations should also consider implementing the ATT&CK framework's mitigation strategies for buffer overflow attacks, including input validation controls and memory protection mechanisms to prevent exploitation of similar vulnerabilities in other software components.