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Fencer Vulns
low 2.7

CVE-2021-25737 json

Holes in EndpointSlice Validation Enable Host Network Hijack

published 2021-09-06 5 y ago modified 2026-06-17 4 mo ago also GHSA-mfv7-gq43-w965 , GO-2022-0908 , EUVD-2021-2095

cvss
2.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

A security issue was discovered in Kubernetes where a user may be able to redirect pod traffic to private networks on a Node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.

Patch / fix

  • go k8s.io/kubernetes 1.18.19, 1.19.11, 1.20.7, 1.21.1
  • kubernetes kubernetes 1.18.19, 1.19.10, 1.20.7
  • kubernetes Debian 14, Debian 13, Debian 12 1.20.5+really1.20.2-1

debian advisories DEBIAN-CVE-2021-25737

  • runc openshift 4.8 1.0.0-98.rhaos4.8.gitcd80260.el7
  • runc openshift 4.8 1.0.0-98.rhaos4.8.gitcd80260.el8
  • cri-o openshift 4.8 1.21.2-5.rhaos4.8.gitb27d974.el7
  • cri-o openshift 4.8 1.21.2-5.rhaos4.8.gitb27d974.el8
  • butane openshift 4.8 0.12.1-1.rhaos4.8.el8
  • ostree openshift 4.8 2020.7-5.el8_4
  • podman openshift 4.8 3.0.1-6.el8
  • haproxy openshift 4.8 2.2.13-1.el7

red hat advisories RHSA-2021:2437

  • govulncheck-vulndb openSUSE Tumbleweed 0.0.20250807T150727-1.1

opensuse advisories openSUSE-SU-2025:15424-1

  • kube-apiserver Arch Linux 1.21.1-1

arch linux advisories AVG-1970

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-25737 updated cvss 2.7

kubernetes: Holes in EndpointSlice Validation Enable Host Network Hijack

  • Red Hat OpenShift Container Platform 4.8 openshift 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el7, openshift 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8, openshift-hyperkube 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el7, openshift-hyperkube 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8
    fixed: vendor fix RHSA-2021:2437
  • Red Hat OpenShift Container Platform 3.11 atomic-openshift, atomic-openshift-pod, atomic-openshift-node, atomic-openshift-tests, atomic-openshift-master, atomic-openshift-clients, +7 more Red Hat OpenShift Container Platform 4.8 podman 3.0.1-6.el8, haproxy 2.2.13-1.el7, haproxy 2.2.13-1.el8, ostree 2020.7-5.el8_4, cri-tools 1.21.0-2.el7, cri-tools 1.21.0-2.el8, +130 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.33% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 2.7 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N
NVD 3.1 4.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.9 AV:N/AC:M/Au:S/C:P/I:P/A:N
GitHub 3.1 4.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
go k8s.io/kubernetes
>=1.16.0, <1.18.19
>=1.19.0, <1.19.11
>=1.20.0, <1.20.7
>=1.21.0, <1.21.1
1.18.19
1.19.11
1.20.7
1.21.1

Affected products

  • Kubernetes Kubernetes

Classification

Weakness
  • CWE-184 Incomplete List of Disallowed Inputs
  • CWE-601 URL Redirection to Untrusted Site
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.