CVE-2026-43417 Details
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.
A vulnerability in the Linux kernel's handling of vfork() with the CLONE_VM flag can lead to scheduling stalls. This issue occurs in the stable branch of the Linux kernel. The problem arises when the number of tasks associated with a process is less than the number of MMCID users. The kernel attempts to fix the CID for vfork()'ed tasks by walking the task list, but the logic is flawed. It double-counts processed tasks, potentially leading to a situation where the vfork()'ed task's CID is not properly restored. As a result, subsequent scheduling operations can fail, causing the system to stall.
Users can upgrade to the latest version of the Linux kernel where this issue has been fixed. Instructions for downloading the patched version are available on the Linux Kernel Archive.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c | kernel.org | Patch |
| https://git.kernel.org/stable/c/e6761cdce78a8919a537989afb6aaf6881469f83 | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| NVD-CWE-noinfo | Insufficient Information to Classify Weakness | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.19, < 6.19.9 7.0 rc1 7.0 rc2 7.0 rc3 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | kernel.org |
| May 22, 2026 | Initial Analysis | [email protected] |
| May 8, 2026 | New CVE Received | kernel.org |