CVE-2021-25741Network attack vector

Host filesystem access via subPath symlink exchange

Published Sep 20, 2021 · Updated Sep 16, 2024

Improper input validation in Kubernetes kubelet 1.22.0 through 1.22.1 allows remote authenticated users to access host files via subPath mounts. Kubelet exchanges symlinks while resolving a container's subPath volume mount, allowing a crafted path to escape the intended volume and reach files or directories on the node. The attacker needs permission to create pods; impact includes host data disclosure and modification, and potentially node service interruption.

CVSS severity8.8
High
EPSS probability7.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Kubernetes kubelet 1.22.0 through 1.22.1 allows remote authenticated users to access host files via subPath mounts. Kubelet exchanges symlinks while resolving a container's subPath volume mount, allowing a crafted path to escape the intended volume and reach files or directories on the node. The attacker needs permission to create pods; impact includes host data disclosure and modification, and potentially node service interruption.

The record

CVE
CVE-2021-25741
Published
Sep 20, 2021
Updated
Sep 16, 2024
Vendor
Kubernetes
Product
Kubernetes
Classifications
CWE-20, T1611
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=1.19.14
  2. Affected versionversion=1.20.0 <=1.20.10
  3. Affected versionversion=1.21.0 <=1.21.4
  4. Affected versionversion=1.22.0 <=1.22.1
  5. Affected versionversion=unspecified <=1.19.14
  6. Affected versionversion=unspecified <=1.20.10
  7. Affected versionversion=unspecified <=1.21.4
  8. Affected versionversion=unspecified <=1.22.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Kubernetes · Kubernetesversion=0 <=1.19.14; version=1.20.0 <=1.20.10; version=1.21.0 <=1.21.4; version=1.22.0 <=1.22.1; version=unspecified <=1.19.14; version=unspecified <=1.20.10; version=unspecified <=1.21.4; version=unspecified <=1.22.1

Published CVSS scores

8.8Kubernetes Security Response CommitteeCVSS:3.1/AV:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20CWE-20: Improper Input Validation
T1611Escape to Host

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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