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Vulnerability record · CVE-2026-64073 · published 19 July 2026

CVE-2026-64073: Linux kernel use after free vulnerability

Linux · Linux Kernel

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.

7.8 CVSS 3.1 High EPSS 0.13% · top 97.7% CWE-416 · Use after free
7.8CVSS 3.1 base score
0.13%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
3 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/18c0456ea2615b1a743a6db739c74411c3b42bc6 Patch
https://git.kernel.org/stable/c/2dc79362302922cb18f35e262712b5e58de65442 Patch
https://git.kernel.org/stable/c/684a78183c54c23e70d1cba320f7fc184604210b Patch
https://git.kernel.org/stable/c/81b582784518196eff1050212a046bc29d3a05dd Patch
https://git.kernel.org/stable/c/91840be8f710370607f949a627e070896faeddb8 Patch
https://git.kernel.org/stable/c/eef4f71b46a9929ac33e968538c9dd5d96a02460 Patch

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Source: NIST National Vulnerability Database (record CVE-2026-64073), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.