CVE-2026-106111 in ImageSharp
Summary
by MITRE • 10/06/2026
ImageSharp is a 2D graphics library. From 4.0.0 until 4.1.2, ExrBaseDecompressor.UndoZipCompression accepts a nonempty ZIP or ZIPS inflate result that is shorter than the EXR block's required size. ZipExrCompression.Decompress reconstructs the returned prefix while ExrDecoderCore processes the full expected block from a buffer obtained through Configuration.Default, allowing bytes retained from a completed prior ImageSharp operation to appear in decoded pixels. Applications that expose pixels or output from the later attacker-controlled EXR decode can disclose process-local image data. This issue is fixed in version 4.1.2.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified within the ImageSharp library, specifically affecting versions ranging from 4.0.0 to 4.1.2, represents a critical information disclosure flaw rooted in improper handling of compressed image data during the decoding process. ImageSharp is widely utilized as a high-performance graphics processing library for .NET applications, and its ability to decode various formats including OpenEXR is essential for many multimedia pipelines. The core issue resides within the ExrBaseDecompressor.UndoZipCompression method, which serves as an intermediate step in decompressing EXR files that utilize ZIP compression schemes. Under normal operational conditions, this function expects a specific relationship between the compressed input data and the resulting uncompressed block size. However, due to insufficient validation logic, the implementation accepts inflate results from ZIP or ZIPS streams where the actual output length is shorter than the required size of the target EXR block. This deviation from expected behavior creates an edge case that disrupts the standard memory management assumptions made by subsequent processing stages.
The technical mechanism of exploitation relies on how the decompressed data is reconstructed and processed in conjunction with global configuration buffers. When ZipExrCompression.Decompress encounters this malformed input, it reconstructs a prefix based on the incomplete inflate result rather than rejecting the invalid block or padding it correctly according to security best practices. This partially filled buffer is then passed to ExrDecoderCore for final processing. Crucially, ExrDecoderCore utilizes Configuration.Default to obtain the working buffer for decoding operations. In many application environments, this default configuration object persists across multiple requests and retains state from previous image processing tasks. Because the decoder expects a full block of data but receives only a partial one due to the vulnerability in UndoZipCompression, it proceeds to process the expected block size by reading beyond the newly provided valid bytes into whatever memory remains allocated for that buffer instance. This results in the inclusion of residual byte sequences from prior ImageSharp operations within the current decoded pixel array.
The operational impact of this flaw is significant, particularly for applications that expose processed image data directly to users or external systems. Since the decoded pixels contain a mixture of new attacker-controlled content and old process-local memory contents, any downstream consumer of these images may inadvertently leak sensitive information. This could include previously processed private images, internal application state represented in pixel formats, or other confidential data stored within the same memory space as long as it has not been overwritten by subsequent operations. For web applications that serve user-uploaded EXR files and return them directly to browsers or APIs without further sanitization, this vulnerability allows an attacker to perform a side-channel style information leak simply by uploading crafted malicious EXR files. The severity is heightened in high-throughput environments where memory buffers are reused frequently, increasing the likelihood of residual data being present when a new decode operation occurs.
From a classification perspective, this vulnerability aligns with CWE-200: Exposure of Sensitive Information to an Unauthorized Actor and CWE-134: Use of Externally-Controlled Format String causing buffer over-read or improper memory access patterns in the context of format parsing. In terms of adversary tactics, it maps to ATT&CK technique T1567.002: Steal Web Session Cookie via Sensitive Information Exposure through crafted input files that trigger unintended data retrieval from server-side resources. The flaw is not a traditional buffer overflow leading to code execution but rather an out-of-bounds read resulting in information leakage, which falls under the broader category of memory safety violations common in systems programming contexts even when managed by higher-level languages like C# if unsafe pointers or specific library behaviors are involved.
Mitigation strategies for this vulnerability primarily involve upgrading the ImageSharp dependency to version 4.1.2 or later, where the developers have implemented stricter validation checks within UndoZipCompression to ensure that decompressed data matches expected block sizes before proceeding with reconstruction and decoding. For organizations unable to immediately upgrade due to compatibility constraints, temporary mitigations include implementing strict input size verification at the application layer before passing EXR files to ImageSharp APIs. Additionally, ensuring that Configuration.Default buffers are cleared or reinitialized between distinct image processing operations can reduce the risk of residual data leakage, although this is a less robust defense than patching the underlying library flaw. Security teams should also audit their usage of ImageSharp for any direct exposure of decoded pixel arrays without additional sanitization steps to minimize the blast radius if similar vulnerabilities are discovered in future versions.