FFmpeg PixelSmash Flaw Allows RCE on Video Players, Media Servers, NAS Appliances

A vulnerability in the FFmpeg media processing framework allows attackers to crash applications and execute arbitrary code remotely, JFrog warns. FFmpeg is used in most media-processing applications across every platform, including desktop video players, Linux file managers, self-hosted media servers, and cloud transcoding pipelines. Tracked as CVE-2026-8461 (CVSS score of 8.8), the security defect is described as a heap out-of-bounds write within FFmpeg’s libavcodec library, in the MagicYUV decoder. The flaw exists in the MagicYUV decoder’s slice handling and is “caused by an inconsistency between how the frame allocator and the decoder compute chroma plane heights,” JFrog explains. Dubbed PixelSmash, it can be exploited to crash any application that uses FFmpeg. Code execution can be achieved by targeting FFmpeg’s AVBuffer struct, a refcounted buffer management object allocated immediately after each plane’s pixel data.  To gain code execution, an attacker needs to target FFmpeg’s AVBuffer struct, a refcounted buffer management object allocated immediately after each plane’s pixel data. According to JFrog, by placing a NUL-terminated shell command at a specific out-of-bounds offset, an attacker can obtain shell execution before the FFmpeg process crashes on subsequent heap corruption. PixelSmash can be exploited for remote code execution (RCE) via crafted media files delivered to any application that uses FFmpeg’s libavcodec for video decoding. On desktop, the vulnerability is triggered when the user opens the malicious file in a video player, or when they browse to a folder containing it, if the file manager’s thumbnail generator uses the vulnerable library. Code execution on a server is achieved when the media file is uploaded to a media server, chat platform, or cloud transcoding service, which automatically processes it. The bug can also be exploited on NAS appliances, media appliances, and smart TVs that generate video thumbnails or previews. “No authentication, special privileges, or prior access to the target system is required beyond the ability to deliver a media file – the default attack surface for any media-processing application,” JFrog explains. The exploit payload can be delivered as a 50 KB AVI, MKV, or MOV file. It can be used in zero-click attacks over torrents if the victim has their torrent client set to download media files directly into a monitored media library folder. As soon as the torrent finishes, the automated library scanning executes the payload. On the self-hosted cloud storage platform Nextcloud, which uses an independent FFmpeg build, the vulnerability can be triggered via the optional Movie preview provider, which invokes the system FFmpeg binary to generate thumbnails. “The attacker requires no interaction beyond ensuring the file is visible in a folder listing; the server-side processing handles the rest, making this a near-zero-click vector,” JFrog notes. The cybersecurity firm confirmed successful exploitation of the bug against Kodi, mpv, ffmpegthumbnailer (used by GNOME, KDE, XFCE), Jellyfin, Emby, Nextcloud, Immich, PhotoPrism, and OBS Studio. It also demonstrated successful RCE against Jellyfin. FFmpeg version 8.1.2 contains fixes for PixelSmash. Users are advised to update as soon as possible. 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