# CVE-2026-43418: linux: In the Linux kernel, the following vulnerability has been resolved:  sched/mmcid: Prevent CID stalls due to concurren...

CVE-2026-43418 is fixed in linux on 1 platform by DEBIAN-CVE-2026-43418 (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-2026-43418
- 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: Prevent CID stalls due to concurrent forks  A newly forked task is accounted as MMCID user before the task is visible in the process' thread list and the global task list. This creates the following problem:   CPU1			CPU2  fork()    sched_mm_cid_fork(tnew1)      tnew1->mm.mm_cid_users++;      tnew1->mm_cid.cid = getcid() -> preemption 			fork() 			  sched_mm_cid_fork(tnew2) 			    tnew2->mm.mm_cid_users++;                             // Reaches the per CPU threshold 			    mm_cid_fixup_tasks_to_cpus() 			    for_each_other(current, p) 			         ....  As tnew1 is not visible yet, this fails to fix up the already allocated CID of tnew1. As a consequence a subsequent schedule in might fail to acquire a (transitional) CID and the machine stalls.  Move the invocation of sched_mm_cid_fork() after the new task becomes visible in the thread and the task list to prevent this.  This also makes it symmetrical vs. exit() where the task is removed as CID user before the task is removed from the thread and task lists.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 6.19.10-1 | [DEBIAN-CVE-2026-43418](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43418.md) | May 15, 2026 |

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Data as of 2026-11-09T01:18:40Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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