CVE-2025-39793

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

io_uring/memmap: cast nr_pages to size_t before shifting

If the allocated size exceeds UINT_MAX, then it's necessary to cast the mr->nr_pages value to size_t to prevent it from overflowing. In practice this isn't much of a concern as the required memory size will have been validated upfront, and accounted to the user. And > 4GB sizes will be necessary to make the lack of a cast a problem, which greatly exceeds normal user locked_vm settings that are generally in the kb to mb range. However, if root is used, then accounting isn't done, and then it's possible to hit this issue.

This vulnerability is rated as Moderate because triggering the integer overflow requires high administrative privileges and abnormal allocation sizes exceeding 4 GB. Standard user accounts are constrained by default memory-locking limits, preventing unprivileged processes from reaching the affected code path. Consequently, exploitation is restricted to local privileged accounts and poses minimal operational threat under standard enterprise deployment models.

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.