# CVE-2025-39793: linux: In the Linux kernel, the following vulnerability has been resolved:  io_uring/memmap: cast nr_pages to size_t before...

CVE-2025-39793 is fixed in linux on 1 platform by DEBIAN-CVE-2025-39793 (version 6.16.3-1), released September 12, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-39793
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0015
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 12, 2025

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 6.16.3-1 | [DEBIAN-CVE-2025-39793](https://patchblox.com/security/data/fix/linux/debian-cve-2025-39793.md) | Sep 12, 2025 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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