CVE-2025-39821Public exploit

Kernel control-flow hijack via inactive perf events

Published Sep 16, 2025 · Updated Sep 16, 2025

Use-after-free in Linux kernel perf event throttling in 6.16 through 6.16.4 allows local users to hijack kernel control flow. perf_event_throttle() and perf_event_unthrottle() start or stop an unscheduled disabled sibling whose hw.idx remains -1, leaving its hrtimer queued after the event is freed. An unprivileged process reaches the flaw through task-scoped perf_event_open() groups at the default paranoid setting, enabling kernel-memory disclosure or corruption, control-flow hijacking, and kernel crashes.

CVSS severity7.8
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel perf event throttling in 6.16 through 6.16.4 allows local users to hijack kernel control flow. perf_event_throttle() and perf_event_unthrottle() start or stop an unscheduled disabled sibling whose hw.idx remains -1, leaving its hrtimer queued after the event is freed. An unprivileged process reaches the flaw through task-scoped perf_event_open() groups at the default paranoid setting, enabling kernel-memory disclosure or corruption, control-flow hijacking, and kernel crashes.

The record

CVE
CVE-2025-39821
Published
Sep 16, 2025
Updated
Sep 16, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.16
  2. Affected versionversion=9734e25fbf5ae68eb04234b2cd14a4b36ab89141 <b64fdd422a85025b5e91ead794db9d3ef970e369
  3. Affected versionversion=9734e25fbf5ae68eb04234b2cd14a4b36ab89141 <d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.16; version=9734e25fbf5ae68eb04234b2cd14a4b36ab89141 <b64fdd422a85025b5e91ead794db9d3ef970e369; version=9734e25fbf5ae68eb04234b2cd14a4b36ab89141 <d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f

Published CVSS scores

7.8Linux Kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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