CVE-2021-4204Public exploit

Kernel code execution via unchecked eBPF ring buffers

Published Aug 24, 2022 · Updated Aug 3, 2024

Out-of-bounds memory access in Linux kernel eBPF 5.8 and later allows local users to crash the system or read kernel memory. The verifier does not learn the allocation size passed to bpf_ringbuf_submit and bpf_ringbuf_discard, allowing crafted pointers to access beyond a ring buffer. Exploitation requires permission to load eBPF programs; successful ring-buffer corruption grants code execution with kernel privileges.

CVSS severity7.1
High
EPSS probability1.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds memory access in Linux kernel eBPF 5.8 and later allows local users to crash the system or read kernel memory. The verifier does not learn the allocation size passed to bpf_ringbuf_submit and bpf_ringbuf_discard, allowing crafted pointers to access beyond a ring buffer. Exploitation requires permission to load eBPF programs; successful ring-buffer corruption grants code execution with kernel privileges.

The record

CVE
CVE-2021-4204
Published
Aug 24, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-119, CWE-20, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 24, 2022CVE 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=Affects Linux kernel v5.8 or later

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=Affects Linux kernel v5.8 or later

Published CVSS scores

7.1CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
7.1NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
7.0OracleCVSS:3.0/AV:L/AC:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-20Improper Input Validation
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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