irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT (CVE-2026-64073) | HOL Guard CVE

High · CVSS 7.8CVE-2026-64073

irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT

Answer in brief

CVE-2026-64073 records a High severity (CVSS 7.8) vulnerability in irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 19, 2026Updated Sep 3, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Sep 3, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.8
Exploitation: Not marked as known exploited
Affected software: 6 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc1::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc2::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc3::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=810979682ccc98dbd83f341c18a2e556c30a7164 <2dc79362302922cb18f35e262712b5e58de65442 \|\| >=810979682ccc98dbd83f341c18a2e556c30a7164 <eef4f71b46a9929ac33e968538c9dd5d96a02460 \|\| >=810979682ccc98dbd83f341c18a2e556c30a7164 <684a78183c54c23e70d1cba320f7fc184604210b \|\| >=810979682ccc98dbd83f341c18a2e556c30a7164 <18c0456ea2615b1a743a6db739c74411c3b42bc6 \|\| >=810979682ccc98dbd83f341c18a2e556c30a7164 <81b582784518196eff1050212a046bc29d3a05dd \|\| >=810979682ccc98dbd83f341c18a2e556c30a7164 <91840be8f710370607f949a627e070896faeddb8	2dc79362302922cb18f35e262712b5e58de65442, eef4f71b46a9929ac33e968538c9dd5d96a02460, 684a78183c54c23e70d1cba320f7fc184604210b, 18c0456ea2615b1a743a6db739c74411c3b42bc6, 81b582784518196eff1050212a046bc29d3a05dd, 91840be8f710370607f949a627e070896faeddb8
Linux/Linuxgeneric	5.16	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 2dc79362302922cb18f35e262712b5e58de65442 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.