---
id: "CVE-2026-99187"
kind: "vulnerability"
aliases: ["CVE-2026-99187"]
title: "Linux kernel perf: PMU migration leaves events behind during CPU hotplug"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "kernel", "linux", "perf"]
not_affected_if: []
published_at: "2026-10-28T11:17:39+00:00"
first_seen_at: "2026-10-28T11:32:37+00:00"
updated_at: "2026-10-28T11:34:16+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99187", "first_seen_at": "2026-10-28T11:32:37+00:00"}]
---

# Linux kernel perf: PMU migration leaves events behind during CPU hotplug

When a CPU is hotplugged, the kernel's perf subsystem can fail to move all of a PMU's performance events to another CPU, leaving some running on the dying CPU. The sources do not describe a direct way for an attacker to gain code execution or data access.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-28T11:32:37+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99187

## From the sources

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

perf: Fix perf_pmu_migrate_context() leaving events behind

__perf_pmu_remove() walks the group leaders of a CPU and PMU with
perf_event_groups_for_cpu_pmu(), removing each one as it goes.
perf_remove_from_context() takes the leader out of the groups rbtree,
after which rb_next() on that node returns NULL, prematurely ending the
walk. Other groups stay behind in the source context.

On CPU hotplug, they are then torn down with the dying CPU. They keep
running until teardown, while the PMU's interrupt and migrated events
are on a new CPU, which drivers rely on never happening.

Walk ctx->event_list instead and pick out the PMU's events by their
pmu_ctx.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_