CVE-2021-25749

ContainerAdministrator execution via case-sensitive username comparison

Published May 24, 2023 · Updated Jan 16, 2025

Improper access control in affected Kubernetes kubelet versions allows local users to run Windows workloads as ContainerAdministrator. Windows runAsNonRoot validation compares the supplied username to ContainerAdministrator case-sensitively, so alternate letter casing bypasses the check while Windows resolves the same account. Exploitation requires permission to create a Windows workload with runAsNonRoot enabled and a crafted runAsUserName, granting administrator rights inside that container.

CVSS severity7.8
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in affected Kubernetes kubelet versions allows local users to run Windows workloads as ContainerAdministrator. Windows runAsNonRoot validation compares the supplied username to ContainerAdministrator case-sensitively, so alternate letter casing bypasses the check while Windows resolves the same account. Exploitation requires permission to create a Windows workload with runAsNonRoot enabled and a crafted runAsUserName, granting administrator rights inside that container.

The record

CVE
CVE-2021-25749
Published
May 24, 2023
Updated
Jan 16, 2025
Vendor
Kubernetes
Product
Kubernetes
Classifications
CWE-284, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 16, 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=kubelet v1.22.0 - v1.22.13 <v1.22.14
  2. Affected versionversion=kubelet v1.23.0 - v1.23.10 <v1.23.11
  3. Affected versionversion=kubelet v1.24.0 - v1.24.4 <v1.24.5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Kubernetes · Kubernetesversion=kubelet v1.22.0 - v1.22.13 <v1.22.14; version=kubelet v1.23.0 - v1.23.10 <v1.23.11; version=kubelet v1.24.0 - v1.24.4 <v1.24.5

Published CVSS scores

7.8Kubernetes CNACVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-284Improper Access Control
T1068Exploitation for Privilege Escalation

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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