CVE-2021-4218

Host reboot via SVC RDMA counter read

Published Aug 24, 2022 · Updated Aug 3, 2024

Denial of service in SVC RDMA sysctl handlers in CentOS Stream kernels allows local users to panic and reboot the host by reading a counter. The read_reset_stat handler passes the kernel buffer supplied by converted sysctl core code to copy_to_user as though it were a user-space pointer. The SVC RDMA module and its readable counter entries must be loaded; triggering the fault interrupts the host until it completes a reboot.

CVSS severity5.5
Medium
EPSS probability0.30%
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 SVC RDMA sysctl handlers in CentOS Stream kernels allows local users to panic and reboot the host by reading a counter. The read_reset_stat handler passes the kernel buffer supplied by converted sysctl core code to copy_to_user as though it were a user-space pointer. The SVC RDMA module and its readable counter entries must be loaded; triggering the fault interrupts the host until it completes a reboot.

The record

CVE
CVE-2021-4218
Published
Aug 24, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-665, T1499
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?

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  1. Affected versionversion=NA

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=NA

Published CVSS scores

4.4SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Canonical UbuntuCVSS: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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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