# CVE-2026-43417: linux: In the Linux kernel, the following vulnerability has been resolved:  sched/mmcid: Handle vfork()/CLONE_VM correctly...

CVE-2026-43417 is fixed in linux on 1 platform by DEBIAN-CVE-2026-43417 (version 6.19.10-1), released May 15, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-43417
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0011
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 8, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  sched/mmcid: Handle vfork()/CLONE_VM correctly  Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in.  It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well.  If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls.  Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 6.19.10-1 | [DEBIAN-CVE-2026-43417](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43417.md) | May 15, 2026 |

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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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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