“Doing the 12-character prefix collision took about 6 hours on my OpenCL-enabled RTX 3080 GPU.”
Linux “Fixes:” tags use a 12-character commit prefix, and 590 commits point at 1da177e4c3f4 alone. Kernel developers pushed back on going to 16 characters because collisions were a “maybe in the future” problem. Kees Cook made one with a gaming GPU in about six hours. The CVE tooling built on those tags broke on contact.