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Response snapshot Nov 5, 2026, 23:11 UTC

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VulnerabilityCVE-2025-38563

Linux kernel: perf/core: Prevent VMA split of buffer mappings

In the Linux kernel, the following vulnerability has been resolved: perf/core: Prevent VMA split of buffer mappings The perf mmap code is careful about mmap()'ing the user page with the ringbuffer and additionally the auxiliary buffer, when the event supports it.

At a glance

Exploited
Not known
Severity
7.8 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2025-38563 (opens a new tab)

What happened

In the Linux kernel, the following vulnerability has been resolved:

perf/core: Prevent VMA split of buffer mappings

The perf mmap code is careful about mmap()'ing the user page with the ringbuffer and additionally the auxiliary buffer, when the event supports it. Once the first mapping is established, subsequent mapping have to use the same offset and the same size in both cases. The reference counting for the ringbuffer and the auxiliary buffer depends on this being correct.

Though perf does not prevent that a related mapping is split via mmap(2), munmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls, which take reference counts, but then the subsequent perf_mmap_close() calls are not longer fulfilling the offset and size checks. This leads to reference count leaks.

Continue reading

As perf already has the requirement for subsequent mappings to match the initial mapping, the obvious consequence is that VMA splits, caused by resizing of a mapping or partial unmapping, have to be prevented.

Implement the vm_operations_struct::may_split() callback and return unconditionally -EINVAL.

That ensures that the mapping offsets and sizes cannot be changed after the fact. Remapping to a different fixed address with the same size is still possible as it takes the references for the new mapping and drops those of the old mapping.

Scores and how they were measured

CVSS base severity

7.8

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2025-38563 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 5). Linux kernel: perf/core: Prevent VMA split of buffer mappings (CVE-2025-38563). https://kevwire.com/record/CVE-2025-38563

MLA

"Linux kernel: perf/core: Prevent VMA split of buffer mappings (CVE-2025-38563)." KEVWire, 5 Nov. 2026, kevwire.com/record/CVE-2025-38563.

Chicago

KEVWire. "Linux kernel: perf/core: Prevent VMA split of buffer mappings (CVE-2025-38563)." Last modified November 5, 2026. https://kevwire.com/record/CVE-2025-38563.

Evidence summary (plain text)

Linux kernel: perf/core: Prevent VMA split of buffer mappings (Aug 19, 2025).
In the Linux kernel, the following vulnerability has been resolved:

perf/core: Prevent VMA split of buffer mappings

The perf mmap code is careful about mmap()'ing the user page with the
ringbuffer and additionally the auxiliary buffer, when the event supports
it. Once the first mapping is established, subsequent mapping have to use
the same offset and the same size in both cases. The reference counting for
the ringbuffer and the auxiliary buffer depends on this being correct.

Though perf does not prevent that a related mapping is split via mmap(2),
munmap(2) or mremap(2).
CVSS 7.8 (version 3.1; evidence as of Nov 5, 2026; https://nvd.nist.gov/vuln/detail/CVE-2025-38563).
Sources:
NVD CVE-2025-38563: https://nvd.nist.gov/vuln/detail/CVE-2025-38563
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-05T21:26:36.106Z&lastModEndDate=2026-11-05T23:10:57.358Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-05T20:51:23.450Z&lastModEndDate=2026-11-05T22:25:57.582Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2025-38563.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 5, 2026, 23:10 UTC. Ingestion is not an independent editorial investigation.

NVD status: Analyzed. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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