# CVE-2025-39951: um: virtio_uml: Fix use-after-free after put_device in probe

CVE-2025-39951 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-39951, released October 4, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-39951
- Priority: High
- CVSS: 7.8 (Moderate)
- EPSS: 0.0015
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 4, 2025
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-39951

## Description

In the Linux kernel, the following vulnerability has been resolved:  um: virtio_uml: Fix use-after-free after put_device in probe  When register_virtio_device() fails in virtio_uml_probe(), the code sets vu_dev->registered = 1 even though the device was not successfully registered. This can lead to use-after-free or other issues.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.158-1 | [DEBIAN-CVE-2025-39951](https://patchblox.com/security/data/fix/linux/debian-cve-2025-39951.md) | Oct 4, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.12.57-1 | [DEBIAN-CVE-2025-39951](https://patchblox.com/security/data/fix/linux/debian-cve-2025-39951.md) | Oct 4, 2025 |
| Linux | linux Debian 14 | 6.16.9-1 | [DEBIAN-CVE-2025-39951](https://patchblox.com/security/data/fix/linux/debian-cve-2025-39951.md) | Oct 4, 2025 |

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Data as of 2026-11-09T19:38:12Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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