CVE-2026-43438 Details
Description
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Remove redundant css_put() in scx_cgroup_init() The iterator css_for_each_descendant_pre() walks the cgroup hierarchy under cgroup_lock(). It does not increment the reference counts on yielded css structs. According to the cgroup documentation, css_put() should only be used to release a reference obtained via css_get() or css_tryget_online(). Since the iterator does not use either of these to acquire a reference, calling css_put() in the error path of scx_cgroup_init() causes a refcount underflow. Remove the unbalanced css_put() to prevent a potential Use-After-Free (UAF) vulnerability.
A Use-After-Free vulnerability has been identified in the Linux kernel's scheduler extension for cgroups, specifically in versions through 6.12. This issue arises from a reference count underflow caused by an improper use of the 'css_put()' function. The 'css_for_each_descendant_pre()' iterator, which traverses the cgroup hierarchy, does not increase the reference counts on the yielded 'css' structures. According to cgroup documentation, 'css_put()' should only be used to release references obtained via 'css_get()' or 'css_tryget_online()'. The erroneous call to 'css_put()' in the error handling of 'scx_cgroup_init()' creates an unbalanced reference count, potentially leading to a Use-After-Free condition.
Users can upgrade to Linux kernel versions 6.12 or later, where this vulnerability has been addressed.
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/1336b579f6079fb8520be03624fcd9ba443c930b | kernel.org | Patch |
| https://git.kernel.org/stable/c/6eaaa67d6998f6c30c462b140db8c062e07ec473 | kernel.org | Patch |
| https://git.kernel.org/stable/c/bf50f3285eda8a0173625fcdb5f183f96e1008cd | kernel.org | Patch |
| https://git.kernel.org/stable/c/cc095cd305fddbe25a968e4a78436ff9476cf0f6 | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-416 | Use After Free | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.12, < 6.12.78 >= 6.13, < 6.18.19 >= 6.19, < 6.19.9 7.0 rc1 7.0 rc2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | kernel.org |
| May 21, 2026 | Initial Analysis | [email protected] |
| May 11, 2026 | CVE Modified | kernel.org |
| May 8, 2026 | New CVE Received | kernel.org |