CVE-2021-33033Public exploit

Local arbitrary write via DOI refcount mishandling

Published May 14, 2021 · Updated Aug 3, 2024

Use-after-free in the Linux kernel before 5.11.14 allows local users to write an arbitrary value through CIPSO label processing. The cipso_v4_genopt function dereferences a DOI definition after CIPSO and CALIPSO code mishandles its reference count. A local user must reach the SMACK/NetLabel socket path; triggering the flaw corrupts kernel memory and interrupts service by crashing the kernel.

CVSS severity7.8
High
EPSS probability0.57%
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 the Linux kernel before 5.11.14 allows local users to write an arbitrary value through CIPSO label processing. The cipso_v4_genopt function dereferences a DOI definition after CIPSO and CALIPSO code mishandles its reference count. A local user must reach the SMACK/NetLabel socket path; triggering the flaw corrupts kernel memory and interrupts service by crashing the kernel.

The record

CVE
CVE-2021-33033
Published
May 14, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 14, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8OracleCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
6.7SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
7.8NVDCVSS: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.

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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 exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
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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