CVE-2021-33630

Kernel crash via unlisted CBS teardown

Published Jan 18, 2024 · Updated May 7, 2025

NULL pointer dereference in the CBS scheduler in openEuler Kernel 4.19.90 before 4.19.90-2401.3 allows local users to crash the kernel. The CBS qdisc initialization path skipped adding offloaded instances to cbs_list, while cbs_destroy later deleted the unlinked list node. Local low-privilege access is required, and the reported consequence is limited to availability through a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the CBS scheduler in openEuler Kernel 4.19.90 before 4.19.90-2401.3 allows local users to crash the kernel. The CBS qdisc initialization path skipped adding offloaded instances to cbs_list, while cbs_destroy later deleted the unlinked list node. Local low-privilege access is required, and the reported consequence is limited to availability through a kernel crash.

The record

CVE
CVE-2021-33630
Published
Jan 18, 2024
Updated
May 7, 2025
Vendor
openEuler
Product
openEuler Kernel
Classifications
CWE-476, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 18, 2024CVE publishedPublication date reported by the CVE source.
  2. May 7, 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=4.19.90 <4.19.90-2401.3 changes=[{"at":"b2239f607df25fc401179e6dd4b7406f942a7632 net/sched: cbs: Fix not adding cbs instance to list","status":"unaffected"}]

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

openEuler · openEuler Kernelversion=4.19.90 <4.19.90-2401.3 changes=[{"at":"b2239f607df25fc401179e6dd4b7406f942a7632 net/sched: cbs: Fix not adding cbs instance to list","status":"unaffected"}]

Published CVSS scores

5.5openEulerCVSS: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 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 exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

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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