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CVE Record

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

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.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel use-after-free flaw in PREEMPT_RT behavior. A local authenticated user could potentially trigger memory corruption with high impact to confidentiality, integrity, and availability. Exposure depends on running an affected Linux kernel with the relevant real-time irq_work path.

Executive priority

Treat as high priority for Linux real-time workloads and multi-user systems. Patch through normal emergency kernel update processes once vendor packages are available, but do not claim internet-wide urgency without exposure evidence.

Technical view

On PREEMPT_RT, non-HARD irq_work runs through per-CPU kthreads. irq_work_single() clears BUSY, then still dereferences work. A concurrent irq_work_sync() caller can observe BUSY cleared, return, and free the object first. The fix keeps irq_work_single() within RCU protection and adds synchronize_rcu() before irq_work_sync() returns.

Likely exposure

Most relevant to Linux systems using PREEMPT_RT or kernels carrying this irq_work implementation. The source bundle names Linux kernel versions and stable commits, but distro package mappings and default RT configuration exposure are not provided.

Exploitation context

The CVSS vector is local, low complexity, low privileges, no user interaction, with high CIA impact. The bundle says KEV is false and provides no evidence of active exploitation or public exploit availability.

Researcher notes

The vulnerable window is after BUSY is cleared in irq_work_single() but before later work dereferences complete. The remediation strategy is lifetime protection with RCU around run_irq_workd() and a grace-period wait in irq_work_sync().

Mitigation direction

  • Apply Linux kernel updates that include the referenced stable fixes.
  • Prioritize systems using PREEMPT_RT or real-time kernels.
  • Reboot systems into the fixed kernel after updating.
  • Check distribution or vendor advisories for exact package names and fixed versions.
  • Use vendor guidance for any temporary mitigation if patching is delayed.

Validation and detection

  • Inventory Linux kernel versions across affected fleets.
  • Identify hosts using PREEMPT_RT or real-time kernel builds.
  • Confirm installed kernels include one of the referenced stable fix commits.
  • Verify systems are booted into the updated kernel, not only patched on disk.
  • Track CVE and vendor advisories for package-specific status.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-64073 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
7Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2026-64073Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux810979682ccc98dbd83f341c18a2e556c30a7164, 810979682ccc98dbd83f341c18a2e556c30a7164, 810979682ccc98dbd83f341c18a2e556c30a7164, 810979682ccc98dbd83f341c18a2e556c30a7164, 810979682ccc98dbd83f341c18a2e556c30a7164, 810979682ccc98dbd83f341c18a2e556c30a7164unaffected
LinuxLinux5.16, 0, 6.1.175, 6.6.142, 6.12.92, 6.18.34, 7.0.11, 7.1affected
Weakness

CWE details

No CWE listed

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