CVE-2026-64073
Received Received - Intake

Use-After-Free in Linux Kernel irq_work

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT On PREEMPT_RT, non-HARD irq_work runs in per-CPU kthreads via run_irq_workd(), so irq_work_sync() uses rcuwait() to wait for BUSY==0. After irq_work_single() clears BUSY via atomic_cmpxchg(), it still dereferences @work for irq_work_is_hard() and rcuwait_wake_up(). An irq_work_sync() caller on another CPU that enters after BUSY is cleared can observe BUSY==0 immediately, return, and free the work before those accesses complete — causing a use-after-free. Fix this by wrapping run_irq_workd() in guard(rcu)() so that the entire irq_work_single() execution is within an RCU read-side critical section. Then add synchronize_rcu() in irq_work_sync() after rcuwait_wait_event() to ensure the caller waits for the RCU grace period before returning, preventing premature frees.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-64073
EUVD
EUVD-2026-45646

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's irq_work subsystem when running on PREEMPT_RT. The issue occurs because irq_work_sync() can return and free memory while another CPU is still accessing the work structure after clearing the BUSY flag. The fix involves wrapping irq_work_single() in an RCU read-side critical section and adding synchronize_rcu() in irq_work_sync() to prevent premature frees.

Detection Guidance

This vulnerability is specific to the Linux kernel's irq_work subsystem on PREEMPT_RT systems. Detection requires checking kernel logs for use-after-free errors or kernel crashes related to irq_work. Commands like dmesg | grep -i "irq_work" or journalctl -k | grep -i "use-after-free" may help identify issues. Ensure your kernel is updated to a patched version.

Impact Analysis

This vulnerability could lead to system crashes, data corruption, or privilege escalation if exploited. Systems running Linux kernels with PREEMPT_RT enabled and using irq_work functionality may be affected. The impact depends on whether the vulnerable code paths are triggered in your specific use case.

Compliance Impact

This vulnerability is a use-after-free issue in the Linux kernel's irq_work subsystem on PREEMPT_RT systems. It does not directly relate to data protection or privacy compliance standards like GDPR or HIPAA, as those focus on data handling, storage, and access controls rather than kernel-level concurrency bugs.

Mitigation Strategies

Apply the latest kernel update from your Linux distribution to patch this vulnerability. If updating is not immediately possible, consider disabling PREEMPT_RT or avoiding workloads that trigger irq_work operations until patched. Monitor kernel logs for signs of exploitation or instability.

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