The setcred(2) system call is only available to privileged users. However, before the privilege level of the caller is checked, the user-supplied list of supplementary groups is copied into a fixed-size kernel stack buffer without first validating its length. If the supplied list exceeds the capacity of that buffer, a stack buffer overflow occurs.

Because the bounds check on the supplementary groups list occurs after the kernel stack buffer has already been written, an unprivileged local user may trigger the overflow without holding any special privilege. Successful exploitation may allow an attacker to execute arbitrary code in the context of the kernel, allowing an unprivileged local user to gain elevated privileges on the affected system.

In order to apply a particular protection key to an address range, the kernel must update the corresponding page table entries. The subroutine which handled this failed to take into account the presence of 1GB largepage mappings created using the shmcreatelargepage(3) interface. In particular, it would always treat a page directory page entry as pointing to another page table page.

The bug can be abused by an unprivileged user to cause pmappkruupdaterange() to treat userspace memory as a page table page, and thus overwrite memory to which the application would otherwise not have access.

Writeup : https://github.com/califio/publications/blob/main/MADBugs/CVE-2026-4747/write-up.md

You mean 4cd93df95e (2025-11-14), then got fixed by the mentioned due to some other problem. Thank you, corrected on the website.