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CVE Record

CVE-2026-23380: tracing: Fix WARN_ON in tracing_buffers_mmap_close

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix WARN_ON in tracing_buffers_mmap_close When a process forks, the child process copies the parent's VMAs but the user_mapped reference count is not incremented. As a result, when both the parent and child processes exit, tracing_buffers_mmap_close() is called twice. On the second call, user_mapped is already 0, causing the function to return -ENODEV and triggering a WARN_ON. Normally, this isn't an issue as the memory is mapped with VM_DONTCOPY set. But this is only a hint, and the application can call madvise(MADVISE_DOFORK) which resets the VM_DONTCOPY flag. When the application does that, it can trigger this issue on fork. Fix it by incrementing the user_mapped reference count without re-mapping the pages in the VMA's open callback.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2026-23380 is a Linux kernel tracing bug where a local process can trigger a kernel warning after fork-related memory mapping behavior. The source documents a fix, but provides no CVSS score, CWE, or confirmed real-world exploitation.

Executive priority

Treat this as a tracking and patch-management item, not an emergency, unless your environment treats kernel warnings as service-impacting events. The available evidence lacks severity scoring, confirmed exploitation, and broader impact analysis.

Technical view

The issue is in tracing_buffers_mmap_close(). A forked child can inherit a VMA without incrementing user_mapped when MADVISE_DOFORK resets VM_DONTCOPY, causing close to run twice and trigger WARN_ON after user_mapped reaches zero. The fix increments user_mapped in the VMA open callback without remapping pages.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions or builds containing the vulnerable tracing change. The bundle lists Linux as affected across versions including 6.10, 6.12.77, 6.18.17, 6.19.7, and 7.0, but distro-specific status is not provided.

Exploitation context

No active exploitation is supported by the provided sources, and the CVE is not marked KEV. The described trigger requires local process behavior involving tracing buffer mmap, madvise(MADVISE_DOFORK), fork, and process exit. The documented outcome is a kernel WARN_ON.

Researcher notes

The key condition is mismatch between VMA inheritance and user_mapped reference counting after MADVISE_DOFORK. Validate only whether affected code exists and whether the stable fix is present; the source bundle does not justify claims of privilege escalation or remote exposure.

Mitigation direction

  • Update to a Linux kernel containing the referenced stable fixes.
  • Check your distribution’s advisory for packaged kernel status.
  • Prioritize self-managed kernels that include the vulnerable tracing change.
  • Do not assume exploitability beyond the documented WARN_ON without vendor analysis.

Validation and detection

  • Inventory Linux kernel versions across servers and appliances.
  • Check whether kernel sources include one of the referenced stable commits.
  • Review distro security advisories for CVE-2026-23380 applicability.
  • Confirm tracing-related kernel updates are deployed and running after reboot.
Prepared
Confidence
medium
Sources
6

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-2026-23380 mapping review

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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
5Source 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
LinuxLinuxcf9f0f7c4c5bb45e7bb270e48bab6f7837825a64, cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64, cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64, cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64unaffected
LinuxLinux6.10, 0, 6.12.77, 6.18.17, 6.19.7, 7.0affected
Weakness

CWE details

No CWE listed

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