CVE-2026-56920 in Android
Summary
by MITRE • 09/15/2026
In s_decode_vui_param of fw_hevc_dec_header.c, there is a possible out-of-bounds write due to a logic error in the code. This could lead to remote code execution with no additional execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability resides within the s_decode_vui_param function located in the fw_hevc_dec_header.c source file, which is part of a firmware-based High Efficiency Video Coding (HEVC) decoder implementation. This specific flaw represents an out-of-bounds write condition triggered by a logic error during the parsing and validation of Video Usability Information parameters. In HEVC streams, VUI data contains metadata that describes how video samples should be displayed, including timing information and bitstream constraints. The decoding process typically involves reading these parameters from the incoming stream and writing them into internal structures or buffers managed by the decoder state machine. When the logic governing this transfer fails to correctly validate input boundaries or handle edge cases in parameter values, it allows an attacker-controlled value to dictate a memory write operation that exceeds the allocated buffer limits. This type of error is fundamentally distinct from simple integer overflows because it stems directly from flawed conditional logic rather than arithmetic miscalculations, yet it results in similar destructive consequences for system integrity.
From a technical perspective, this out-of-bounds write enables an attacker to corrupt adjacent memory regions that are critical to the execution flow or security controls of the firmware environment. Since HEVC decoding is often performed on network-received video streams, such as those used in surveillance systems, streaming platforms, or embedded IoT devices with display capabilities, the attack vector is highly accessible. The absence of required user interaction means that an attacker can trigger this vulnerability simply by delivering a maliciously crafted HEVC stream to the target system. This could be achieved through various methods including hosting a compromised video file on a website visited via auto-play features, injecting malformed packets into a live streaming feed, or exploiting networked media players that automatically process incoming data without explicit user confirmation for each frame. The lack of additional execution privileges required further lowers the barrier to entry, allowing unauthenticated remote attackers to exploit this flaw against any system running the affected firmware version.
The operational impact of successfully exploiting this vulnerability is severe and potentially catastrophic. An out-of-bounds write in a low-level video decoding component typically allows for arbitrary code execution with the same privileges as the vulnerable process. In many embedded or firmware contexts, these processes run with high-level administrative rights to access hardware resources directly. Consequently, an attacker can gain full control over the device, install persistent backdoors, exfiltrate sensitive data such as recorded surveillance footage, or use the compromised device as a pivot point for further network attacks. The stability of the system is also at risk; while exploitation aims for code execution, improper memory corruption often leads to immediate crashes or denial-of-service conditions that disrupt critical services relying on video processing capabilities.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-787, which classifies out-of-bounds writes as a category of memory safety errors where data is written beyond the intended buffer boundary. It also maps closely to MITRE ATT&CK technique T1203, specifically the exploitation phase for client-side attacks or software execution via vulnerable components. The fact that it requires no user interaction places it in high-severity categories within most vulnerability scoring systems due to its remote exploitability and lack of authentication prerequisites. Mitigation strategies must focus on rigorous input validation at the point where VUI parameters are extracted from the bitstream. Developers should implement strict bounds checking before any memory write operations occur, ensuring that all indices calculated based on stream data remain within valid ranges defined by the buffer size. Additionally, employing static analysis tools capable of detecting logic errors in C/C++ codebases and conducting fuzzing tests against HEVC parsers can help identify similar flaws early in the development lifecycle. Firmware updates should prioritize patching this specific function to enforce safe memory access patterns and prevent remote attackers from achieving arbitrary code execution through malformed video streams.