CVE-2026-75142 in FFmpeg
Summary
by MITRE • 08/19/2026
FFmpeg before commit 9d786e4 contains a stack buffer overflow in the MPEG-PS muxer (libavformat/mpegenc.c). When muxing input with more streams than the muxer's fixed-size stack buffer accommodates, the buffer is overflowed. A crafted input with an excessive number of streams triggers the overflow during MPEG-PS muxing.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified in FFmpeg prior to commit 9d786e4 represents a critical memory safety failure within the MPEG Program Stream (MPEG-PS) multiplexer, specifically located in the libavformat/mpegenc.c module. This flaw is classified as a stack-based buffer overflow, which corresponds directly to CWE-121: Stack-based Buffer Overflow. The root cause lies in the muxer's handling of input streams during the construction of MPEG-PS containers. FFmpeg utilizes fixed-size buffers on the call stack for various internal operations related to stream management and header generation. In this specific instance, the code fails to perform adequate bounds checking when iterating over or processing an excessive number of input streams. Instead of dynamically allocating memory based on the actual count of streams or validating that the operation will fit within the pre-allocated static buffer size, the implementation assumes a maximum capacity that is not enforced by runtime checks.
When a user provides a crafted media file containing more audio and video tracks than the muxer's internal stack buffer can accommodate, the writing process exceeds the allocated memory space on the stack. This overflow overwrites adjacent memory locations, which may include return addresses, saved frame pointers, or other critical control data structures stored on the call stack. The operational impact of this vulnerability is severe, as it allows for arbitrary code execution under certain conditions. An attacker who can trick a victim into processing a maliciously crafted MPEG-PS file with an unusually high number of streams could trigger this overflow during the muxing process. This typically occurs when FFmpeg is used in a server-side capacity to transcode or repack media files, where untrusted input is processed automatically without manual review by security personnel.
From a threat intelligence perspective, this vulnerability aligns with ATT&CK technique T1203: Exploitation for Client Execution if the victim uses a client application that relies on FFmpeg libraries to handle video processing tasks locally. It also relates to CWE-787: Out-of-bounds Write in broader contexts of memory corruption vulnerabilities. The exploitation potential is heightened by the fact that stack buffer overflows are well-understood attack vectors with established exploit development techniques, including return-oriented programming (ROP) chains or direct shellcode injection depending on compiler protections such as Stack Canaries and Address Space Layout Randomization (ASLR). If these mitigations are not fully effective or if specific memory layouts allow for predictable control flow hijacking, the attacker gains full privilege level of the compromised process.
Mitigation strategies primarily involve updating FFmpeg to a version that includes commit 9d786e4 or later, which addresses this issue by implementing proper bounds checking and potentially switching to heap allocation for variable-length stream data structures where appropriate. For organizations unable to immediately patch their systems, defensive measures should include input validation at the application layer to limit the number of streams accepted during muxing operations. Additionally, deploying runtime protection mechanisms such as Data Execution Prevention (DEP) and ensuring that modern compiler flags are enabled can reduce the likelihood of successful exploitation. Security teams should also monitor for unusual memory access patterns or crashes in media processing services, which may indicate attempted exploitation of this stack-based overflow vulnerability.