CVE-2026-106117 in ImageSharp
Summary
by MITRE • 10/06/2026
ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, decoding a strip TIFF using CCITT Group 3 or Modified Huffman compression can pass attacker-expanded runs to BitWriterUtils.WriteBits without first checking the current row width. T4TiffCompression.WritePixelRun can accumulate oversized makeup-code runs, and ModifiedHuffmanTiffCompression.Decompress validates the width only after writing. The unchecked writes can overflow the strip buffer, corrupt heap memory, and terminate the process. This strip-path vulnerability is distinct from the tiled decompressor-width mismatch. This issue is fixed in version 4.1.1.
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Analysis
by VulDB Data Team • 10/06/2026
ImageSharp versions ranging from 3.0.0 through 4.1.1 contain a critical buffer overflow vulnerability within its TIFF image decoding logic, specifically affecting images compressed with CCITT Group 3 or Modified Huffman compression schemes. This flaw arises during the processing of strip-based TIFF files where the library fails to validate row dimensions prior to writing pixel data into memory buffers. The core technical deficiency lies in the interaction between T4TiffCompression.WritePixelRun and BitWriterUtils.WriteBits, where oversized makeup-code runs generated by an attacker-controlled input can be passed directly to the bit writer without verifying that they fit within the allocated strip buffer boundaries. In the Modified Huffman compression path, while width validation exists, it is performed only after the pixel data has already been written, rendering the check ineffective at preventing memory corruption.
The operational impact of this vulnerability is severe, as the unchecked writes can lead to heap-based buffer overflows that corrupt adjacent memory structures and potentially allow for arbitrary code execution if exploited in a context where memory layout is controllable by an attacker. Even without remote code execution, the immediate consequence is often process termination due to access violations or stack corruption triggered by the out-of-bounds write operations. This specific strip-path vulnerability is distinct from other known issues involving tiled decompressor width mismatches, indicating that different code paths within the library were affected and required separate remediation efforts. The lack of proper bounds checking during the decomposition phase allows maliciously crafted TIFF files to trigger these memory safety violations upon parsing.
From a classification perspective, this issue aligns with CWE-120 Buffer Copy without Checking Size of Input Classic buffer overflow and CWE-787 Out-of-bounds Write, as the root cause is writing data beyond the intended limits of a allocated buffer due to insufficient validation of input dimensions. In terms of attack vectors, an adversary could leverage this flaw through ATT&CK technique T1059 Command and Scripting Interpreter if they can induce execution flow changes via memory corruption, or more commonly in library contexts, it represents a denial-of-service vector under T1499 Endpoint Denial of Service by causing application crashes. The vulnerability highlights the importance of rigorous input validation at every stage of data processing, particularly when handling complex binary formats like TIFF that involve multiple compression algorithms and decoding paths.
To mitigate this risk, organizations utilizing ImageSharp must upgrade to version 4.1.1 or later where these checks have been properly implemented before memory writes occur. For systems unable to immediately patch, implementing strict input validation at the application layer to reject malformed TIFF files with suspiciously large run lengths can provide a temporary defense-in-depth measure. Additionally, enabling runtime protection mechanisms such as Address Space Layout Randomization and heap hardening features in modern operating systems may help mitigate exploitation attempts by making memory corruption less predictable for attackers. Regular security audits of third-party dependencies are essential to identify similar vulnerabilities in other graphics processing libraries that handle untrusted image inputs.