CVE-2021-25740

Holes in EndpointSlice Validation Enable Host Network Hijack

3.1 LowFix available

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: None
Availability: None

Exploit likelihood

1.95%Up 1.3 points since Sep 21, 2021

What each source reports

CVE List Score used 3.1

Holes in EndpointSlice Validation Enable Host Network Hijack

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: CVE-2021-25740
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-441
Updated: 2026-11-02

EUVDEUVD-2021-2120 3.1

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: EUVD-2021-2120
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-vw47-mr44-3jf9 3.1

Confused Deputy in Kubernetes

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: GHSA-vw47-mr44-3jf9
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-441, CWE-610
Updated: 2026-11-02

NVD 3.1

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: CVE-2021-25740
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS 2.0: 3.5 LowAV:N/AC:M/Au:S/C:P/I:N/A:N
Weakness: CWE-441, CWE-610
Updated: 2026-11-02

OSVAZL-89312 3.1

CVE-2021-25740 affecting package kubernetes 1.30.10-32

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: AZL-89312
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-05

OSV 3.1

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: CVE-2021-25740
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

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OSVDEBIAN-CVE-2021-25740 3.1

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: DEBIAN-CVE-2021-25740
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

OSVGHSA-vw47-mr44-3jf9 3.1

Confused Deputy in Kubernetes

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: GHSA-vw47-mr44-3jf9
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-441, CWE-610
Updated: 2026-11-02

OSVOESA-2022-2139 3.1

kubernetes security update

Container cluster management.

Security Fix(es):

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.(CVE-2021-25740)

Record: OESA-2022-2139
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-25740 3.1

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Record: UBUNTU-CVE-2021-25740
CVSS 3.1: 3.1 LowCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-02

Affected products

kubernetes

Affected packages

Affected packages
Package	Affected	Fixed
`k8s.io/kubernetes` Go	through 1.22.2	None known
`kubernetes` Azure Linux:3	through 1.30.10-32	None known
`kubernetes` Debian:12	before 1.20.5+really1.20.2-1	1.20.5+really1.20.2-1
`kubernetes` Debian:13	before 1.20.5+really1.20.2-1	1.20.5+really1.20.2-1
`kubernetes` Debian:14	before 1.20.5+really1.20.2-1	1.20.5+really1.20.2-1
`kubernetes` openEuler:20.03-LTS-SP1	before 1.20.2-16.oe1	1.20.2-16.oe1

History

History
Recorded	Changed	Sources
Nov 5, 2026	facts	OSV
Nov 3, 2026	affected
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-25740 is a low vulnerability (CVSS 3.1) in Kubernetes, published September 20, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.95%, the 80th percentile. Fixed in kubernetes 1.20.5+really1.20.2-1.

References

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