CVE-2026-8461 in FFMPEG 8.1.1 (needs an update to 8.1.2)

[aremishevsky]

Please update FFMPEG 8.1.1 up to 8.1.2 version to resolve the CVE-2026-8461
https://github.com/search?q=repo%3Aopencv%2Fopencv-python+FFMPEG_VERSION&type=code

Here is the CVE: https://nvd.nist.gov/vuln/detail/CVE-2026-8461

[MDSALMANSHAMS]

CVE-2026-8461 is an out-of-bounds write in ffmpeg's MagicYUV decoder (libavcodec/magicyuv.c, CWE-787, CVSS 8.8), fixed upstream in 8.1.2.

All seven build Dockerfiles are currently pinned at ARG FFMPEG_VERSION=8.1.1 - manylinux2014 (i686, x86_64, aarch64), manylinux_2_28 (x86_64, aarch64) and musllinux_1_2 (x86_64, aarch64). I'll put up a PR bumping all of them to 8.1.2; I did the 8.1.1 i686 bump in #1233.

Confirmed ffmpeg-8.1.2.tar.gz is published on ffmpeg.org (8.1.3 is not released), so the existing download URLs resolve unchanged.