CVE-2021-3679

Denial of service via stale ring-buffer pointer

Published Aug 5, 2021 · Updated Aug 3, 2024

Denial of service in Linux Kernel before 5.14-rc3 allows local users with CAP_SYS_ADMIN to consume a CPU through the tracing ring buffer. The rb_per_cpu_empty() check uses a stale read pointer, leaving tracing_read_pipe() indefinitely polling an empty buffer. Control of tracefs through root or CAP_SYS_ADMIN is required; the trapped process remains running, drains CPU resources, and cannot be terminated even with SIGKILL.

CVSS severity5.5
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux Kernel before 5.14-rc3 allows local users with CAP_SYS_ADMIN to consume a CPU through the tracing ring buffer. The rb_per_cpu_empty() check uses a stale read pointer, leaving tracing_read_pipe() indefinitely polling an empty buffer. Control of tracefs through root or CAP_SYS_ADMIN is required; the trapped process remains running, drains CPU resources, and cannot be terminated even with SIGKILL.

The record

CVE
CVE-2021-3679
Published
Aug 5, 2021
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-400, CWE-835, T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Aug 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=kernel 5.14-rc3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.14-rc3

Published CVSS scores

2.1National Institute of Standards and TechnologyAV:L/AC:L/Au:N/C:N/I:N/A:P
5.5National Institute of Standards and TechnologyCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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