CVE-2025-21863

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

io_uring: prevent opcode speculation

sqe->opcode is used for different tables, make sure we santitise it against speculations.

This vulnerability is rated with a Moderate severity because exploitation is restricted to authenticated local users who can submit crafted io_uring requests, allowing potential speculative side-channel observation of kernel memory. Because this issue involves speculative execution (Spectre-style bounds check bypass) rather than direct memory corruption or remote execution, it cannot be leveraged directly for unauthorized modification or system disruption. Earlier enterprise releases such as Red Hat Enterprise Linux 8 do not incorporate the affected opcode indexing logic and remain unaffected.

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.