CVE Catalog

CVE-2026-64211

MediumCVSS 5.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.16%

5th percentile - higher than 5% of all known CVEs

Summary

In the Linux kernel's SRCU mechanism, during a state transition from CPU-0 to all-CPUs, workqueue handlers may be queued on CPUs that have never been online, causing hangs on s390 systems.

Risk Assessment

Queuing work on non-existent CPUs can cause system hangs, especially on s390, which is not designed to handle such scenarios.

Recommendation

Apply the patch that prevents queuing workqueue handlers on never-online CPUs and redirects callbacks from not-yet-online CPUs to the boot CPU.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: srcu: Don't queue workqueue handlers to never-online CPUs While an srcu_struct structure is in the midst of switching from CPU-0 to all-CPUs state, it can attempt to invoke callbacks for CPUs that have never been online. Worse yet, it can attempt in invoke callbacks for CPUs that never will be online, even including imaginary CPUs not in cpu_possible_mask. This can cause hangs on s390, which is not set up to deal with workqueue handlers being scheduled on such CPUs. This commit therefore causes Tree SRCU to refrain from queueing workqueue handlers on CPUs that have not yet (and might never) come online. Because callbacks are not invoked on CPUs that have not been online, it is an error to invoke call_srcu(), synchronize_srcu(), or synchronize_srcu_expedited() on a CPU that is not yet fully online. However, it turns out to be less code to redirect the callbacks from too-early invocations of call_srcu() than to warn about such invocations. This commit therefore also redirects callbacks queued on not-yet-fully-online CPUs to the boot CPU.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS