Medium [CVE-2026-64073] Fix use-after-free in irq_work_single on PREEMPT_RT
This medium-severity Red Hat Linux advisory covers CVE-2026-64073 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
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.
A flaw was found in the Linux kernel, specifically within the `irq_work` subsystem when running on systems configured with PREEMPT_RT. This vulnerability is a use-after-free, where the system attempts to access memory after it has been released.
A local attacker could exploit this timing issue to cause a system crash, leading to a denial of service. In some scenarios, this type of flaw could potentially be leveraged for arbitrary code execution.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
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