CVE-2025-59733 in FFmpeg
Summary
by MITRE • 10/06/2025
When decoding an OpenEXR file that uses DWAA or DWAB compression, there's an implicit assumption that all image channels have the same pixel type (and size), and that if there are four channels, the first four are "B", "G", "R" and "A". The channel parsing code can be found in decode_header. The buffer td->uncompressed_data is allocated in decode_block based on the xsize, ysize and computed current_channel_offset.
The function dwa_uncompress then assumes at [5] that if there are 4 channels, these are "B", "G", "R" and "A", and in the calculations at [6] and [7] that all channels are of the same type, which matches the type of the main color channels.
If we set the main color channels to a 4-byte type and add duplicate or unknown channels of the 2-byte EXR_HALF type, then the addition at [7] will increment the pointer by 4-bytes * xsize * nb_channels, which will exceed the allocated buffer.
We recommend upgrading to version 8.0 or beyond.
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Analysis
by VulDB Data Team • 06/21/2026
The vulnerability described in CVE-2025-59733 represents a critical buffer overflow condition within OpenEXR file processing libraries that specifically affects files utilizing DWAA or DWAB compression formats. This issue stems from a fundamental assumption in the decoding logic that all image channels within a compressed file maintain identical pixel types and sizes, creating a dangerous mismatch between memory allocation and actual data processing. The flaw manifests in the channel parsing mechanism located within the decode_header function, where the system incorrectly presumes uniform channel characteristics across all data elements, particularly when dealing with multi-channel image formats.
The technical implementation of this vulnerability occurs through a cascading series of memory management errors that begin with the allocation of the td->uncompressed_data buffer within the decode_block function. This buffer allocation is calculated based on the image dimensions xsize and ysize along with a computed current_channel_offset value that determines the total memory required for decompression operations. However, the subsequent dwa_uncompress function contains a critical assumption at line [5] that when four channels are present, they must be ordered as "B", "G", "R", and "A" respectively, without proper validation of channel type consistency. The vulnerability becomes apparent when the system encounters files where main color channels are configured as 4-byte types while additional channels are specified as 2-byte EXR_HALF types, creating a scenario where pointer arithmetic calculations at lines [6] and [7] incorrectly assume all channels share the same type as the primary color channels.
The operational impact of this vulnerability extends beyond simple memory corruption, creating potential attack vectors that align with multiple ATT&CK techniques including privilege escalation through memory corruption and resource exploitation. When the system attempts to process these malformed files, the pointer arithmetic operations increment the buffer pointer by 4 bytes per pixel multiplied by the total number of channels, causing the decompression process to write beyond the allocated memory boundaries. This memory corruption can lead to arbitrary code execution, application crashes, or data integrity issues that compromise the entire image processing pipeline. The vulnerability specifically targets the buffer overflow category as classified by CWE-121, where insufficient protection mechanisms exist to prevent memory access beyond allocated bounds.
The recommended mitigation strategy involves upgrading to version 8.0 or later, which addresses the fundamental assumptions in the channel parsing logic and implements proper validation of channel type consistency before memory allocation occurs. This upgrade should include enhanced bounds checking mechanisms and more robust channel type validation that prevents the scenario where different channel types are processed under the assumption of uniformity. Organizations should also implement defensive programming practices such as input validation, memory safety checks, and regular security assessments of their OpenEXR processing systems to prevent exploitation of similar vulnerabilities. The fix should incorporate proper error handling for channel type mismatches and ensure that buffer allocation accounts for actual channel type variations rather than relying on assumptions about channel ordering and uniformity.