CVE-2025-39793
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
In the Linux kernel's io_uring/memmap subsystem, nr_pages was not cast to size_t before shifting, potentially causing overflow for allocations exceeding 4 GB. This issue primarily affects root users, as memory accounting is not performed for them.
Risk Assessment
The organization may face page counter overflow during large memory allocations, potentially leading to unpredictable system behavior, especially when using the root account.
Recommendation
It is recommended to update the Linux kernel to a version that casts nr_pages to size_t before shifting to prevent overflow.
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Original NVD description (English source)
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.