CVE-2025-21836

In the Linux kernel, the following vulnerability has been resolved:

io_uring/kbuf: reallocate buf lists on upgrade

IORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it was created for legacy selected buffer and has been emptied. It violates the requirement that most of the field should stay stable after publish. Always reallocate it instead.

This vulnerability is rated as Moderate severity because exploitation requires local access to interact with the io_uring subsystem and primarily poses a risk of denial of service via kernel crashes. A local user must be able to register provided buffer rings to trigger the improper reuse condition. Earlier enterprise releases such as Red Hat Enterprise Linux 8 do not contain the affected code and are not impacted.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.