CVE-2026-70629 in FFmpeg
Summary
by MITRE • 08/07/2026
FFmpeg versions from 3.0 up to, but not including, 9.0 contain an uninitialized heap memory read vulnerability in the native RSCC decoder (libavcodec/rscc.c) that allows attackers to disclose heap memory contents by supplying a crafted video file with a compressed tile that decompresses fewer bytes than the declared tile geometry requires. When rscc_decode_frame() calls av_image_copy_plane() without validating the decompressed byte count against the tile dimensions, the unwritten suffix of the persistent intermediate buffer ctx->inflated_buf is copied into the decoded frame, potentially exposing data from prior heap allocations or previous decoded frames in persistent decoding services.
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Analysis
by VulDB Data Team • 08/07/2026
This vulnerability resides within the FFmpeg multimedia processing library where an uninitialized heap memory read flaw exists in the native RSCC (RSCC stands for Real-time Streaming Compression Codec) decoder implementation. The vulnerability affects versions starting from 3.0 through 8.x but not including version 9.0, representing a critical security risk that can be exploited by remote attackers through specially crafted video files. The flaw manifests when the rscc_decode_frame() function processes compressed tiles without proper validation of decompressed byte counts against declared tile geometry requirements. This issue stems from inadequate input sanitization and buffer boundary checking mechanisms within the decoding pipeline.
The technical exploitation occurs when av_image_copy_plane() is invoked without validating whether the actual decompressed data size matches the expected tile dimensions. The RSCC decoder maintains a persistent intermediate buffer ctx->inflated_buf that stores decompressed frame data across multiple decode operations. When the decompression process generates fewer bytes than declared by the tile geometry, portions of this persistent buffer remain uninitialized or contain stale data from previous operations. During subsequent frame copying operations, these unwritten memory segments are inadvertently included in the final decoded output, creating a memory disclosure vulnerability that can expose sensitive information from heap allocations.
This vulnerability directly maps to CWE-125: Uninitialized Memory Read within the Common Weakness Enumeration framework, specifically targeting memory safety issues in multimedia processing libraries. The operational impact extends beyond simple information disclosure as it can potentially reveal cryptographic keys, user credentials, or other sensitive data that may have resided in previously allocated heap memory segments. Attackers can craft malicious video files that trigger this condition by manipulating the compressed tile metadata to declare larger dimensions than the actual decompressed data content provides. The vulnerability is particularly concerning in persistent decoding services where multiple frames are processed sequentially, as each frame processing operation may expose previously decoded or allocated memory contents.
The ATT&CK framework categorizes this vulnerability under T1590: Indicator Removal on Target System and T1203: Exploitation for Client Execution, as it enables attackers to gather intelligence about system memory layout and potentially extract sensitive information from heap allocations. The risk is amplified in environments where FFmpeg processes untrusted video content such as web browsers, media servers, or content management systems that may cache decoded frames. Mitigation strategies should include immediate version upgrades to FFmpeg 9.0 or later where the vulnerability has been patched, implementing strict input validation for all media file processing pipelines, and deploying memory sanitization tools to detect similar uninitialized memory access patterns. Additionally, organizations should consider network segmentation and content filtering mechanisms to prevent exploitation through malicious media files in environments where media processing is not strictly controlled.