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CVE Record

CVE-2026-23134: slab: fix kmalloc_nolock() context check for PREEMPT_RT

In the Linux kernel, the following vulnerability has been resolved: slab: fix kmalloc_nolock() context check for PREEMPT_RT On PREEMPT_RT kernels, local_lock becomes a sleeping lock. The current check in kmalloc_nolock() only verifies we're not in NMI or hard IRQ context, but misses the case where preemption is disabled. When a BPF program runs from a tracepoint with preemption disabled (preempt_count > 0), kmalloc_nolock() proceeds to call local_lock_irqsave() which attempts to acquire a sleeping lock, triggering: BUG: sleeping function called from invalid context in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6128 preempt_count: 2, expected: 0 Fix this by checking !preemptible() on PREEMPT_RT, which directly expresses the constraint that we cannot take a sleeping lock when preemption is disabled. This encompasses the previous checks for NMI and hard IRQ contexts while also catching cases where preemption is disabled.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects PREEMPT_RT real-time kernels. A memory allocation path can wrongly try to take a sleeping lock while preemption is disabled, causing a kernel BUG condition. The source bundle does not provide CVSS, CWE, privilege requirements, or a confirmed security impact beyond kernel instability.

Executive priority

Treat as a targeted kernel maintenance item. It is most urgent for real-time Linux environments where kernel BUG conditions can disrupt operations, but the public record does not support emergency response claims.

Technical view

kmalloc_nolock() only checked NMI and hard IRQ context. On PREEMPT_RT, local_lock may sleep, so callers with preemption disabled, including BPF tracepoint execution, can trigger an invalid sleeping-lock acquisition. The fix adds a PREEMPT_RT !preemptible() check before using local_lock_irqsave().

Likely exposure

Exposure appears limited to Linux systems running affected PREEMPT_RT kernel versions or commit ranges. The provided data lists Linux 6.18, 6.18.8, and 6.19 as affected, but distro backport status is not included.

Exploitation context

The bundle does not cite active exploitation, and KEV is false. It describes a trigger involving a BPF program running from a tracepoint with preemption disabled, but does not establish attacker prerequisites or remote exploitability.

Researcher notes

The public bundle is sparse: no CVSS, CWE, privilege model, exploit status, or distro matrix. Analysis should stay tied to PREEMPT_RT behavior and the two kernel stable commits until vendors publish broader guidance.

Mitigation direction

  • Apply vendor or distro kernel updates containing the referenced stable fixes.
  • Prioritize PREEMPT_RT systems and hosts using BPF tracing workloads.
  • Check vendor advisories before assuming generic kernel version numbers are affected.
  • Plan maintenance windows for real-time workloads before kernel replacement.

Validation and detection

  • Inventory systems running PREEMPT_RT kernels in the listed affected ranges.
  • Confirm kernel packages include commits f60ba4a97ae3 or 99a3e3a1cfc9.
  • Review kernel logs for invalid-context sleeping function BUG messages.
  • Check BPF tracepoint usage on real-time systems for exposure prioritization.
Prepared
Confidence
medium
Sources
4

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

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

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

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
LinuxLinuxaf92793e52c3a99b828ed4bdd277fd3e11c18d08, af92793e52c3a99b828ed4bdd277fd3e11c18d08unaffected
LinuxLinux6.18, 0, 6.18.8, 6.19affected
Weakness

CWE details

No CWE listed

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