CVE-2026-68513 in OpenEXR
Summary
by MITRE • 08/25/2026
OpenEXR is the reference implementation and specification for the EXR image format, widely used in the motion picture industry. Versions 3.3.0 through 3.3.12 and 3.4.0 through 3.4.13 contain a heap buffer overflow in PyOpenEXR triggered by a channel-name key collision between literal and prefixed RGB channels. When separate_channels=false, PyOpenEXR maps each physical channel name through channelNameToRGBA() and coalesces the results into a shared RGB array. A crafted flat scanline EXR that contains both a literal channel such as left and prefixed channels such as left.R, left.G, and left.B causes these names to collide, so the wrapper reuses an undersized two-dimensional NumPy array for the coalesced RGB slices and writes out of bounds when OpenEXR.File(path) decodes the pixels. This issue is fixed in versions 3.3.13 and 3.4.14.
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Analysis
by VulDB Data Team • 08/25/2026
OpenEXR serves as the reference implementation and specification for the EXR image format, a standard widely adopted within the motion picture industry for high-dynamic-range imaging and visual effects workflows. The PyOpenEXR library provides Python bindings that allow developers to read and write these complex image files programmatically. A critical security vulnerability has been identified in versions 3.3.0 through 3.3.12 and 3.4.0 through 3.4.13 of this software, specifically affecting the handling of channel data when certain configuration options are enabled. This flaw manifests as a heap buffer overflow, which poses significant risks to application stability and potentially allows for arbitrary code execution if exploited by an attacker controlling the input file content.
The technical root cause lies in how PyOpenEXR processes channel names during image decoding when the separate_channels parameter is set to false. In this mode, the library attempts to map each physical channel name through a function called channelNameToRGBA and coalesce the results into a shared RGB array for efficient processing. The vulnerability arises from an incorrect assumption regarding channel naming conventions. Specifically, if a crafted flat scanline EXR file contains both literal channel names, such as left, and prefixed channels like left.R, left.G, and left.B, these distinct logical entities are treated as colliding keys within the internal mapping logic. This collision causes the wrapper to incorrectly reuse an undersized two-dimensional NumPy array intended for coalesced RGB slices.
When OpenEXR.File decodes the pixels from such a maliciously crafted file, it attempts to write pixel data into this improperly sized buffer. Because the allocated memory space is insufficient to hold the combined data of all conflicting channels, the operation results in writing beyond the bounds of the heap-allocated array. This out-of-bounds write constitutes a classic heap buffer overflow vulnerability. Such flaws can lead to memory corruption, application crashes due to segmentation faults, or more severe consequences where an attacker might leverage the overwritten memory to execute arbitrary code with the privileges of the running process. The impact is particularly relevant for applications that automatically process untrusted image inputs without rigorous validation prior to parsing.
From a classification perspective, this vulnerability aligns with CWE-120, which describes buffer copy without checking size limits, and more specifically CWE-787, indicating out-of-bounds write access. In the context of attack vectors, it relates to ATT&CK technique T1203, exploitation for defense evasion or execution via vulnerable components, as well as general input validation failures often categorized under improper neutralization of special elements used in an injection (CWE-74) if the overflow leads to further memory manipulation. The flaw highlights the importance of robust boundary checking and distinct namespace management when handling structured data formats that allow for complex naming schemes.
To mitigate this risk, organizations relying on PyOpenEXR must upgrade immediately to version 3.3.13 or later, where the issue has been resolved by correcting the channel name collision logic and ensuring proper memory allocation based on actual channel requirements rather than assumed collisions. Until an update can be applied, defensive measures should include implementing strict input validation at the application layer to reject EXR files that contain conflicting literal and prefixed channel names before they are passed to the OpenEXR decoder. Additionally, deploying runtime protection mechanisms such as heap hardening techniques or sandboxing environments where PyOpenEXR operates can help limit the impact of any potential exploitation attempts by containing memory corruption events within isolated processes.