CVE-2021-3636

In-cluster service impersonation via overbroad CA bundle

Published Jul 30, 2021 · Updated Aug 3, 2024

Improper certificate validation in Red Hat OpenShift Container Platform before 4.8 allows attackers to impersonate trusted in-cluster services. The injected service-ca.crt trust bundle includes ingress and other internal CAs instead of only the service-serving signer. Upgraded 4.8 clusters can retain the legacy bundle; exploitation requires control of an included CA and can expose or alter trusted traffic.

CVSS severity4.6
Medium
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Red Hat OpenShift Container Platform before 4.8 allows attackers to impersonate trusted in-cluster services. The injected service-ca.crt trust bundle includes ingress and other internal CAs instead of only the service-serving signer. Upgraded 4.8 clusters can retain the legacy bundle; exploitation requires control of an included CA and can expose or alter trusted traffic.

The record

CVE
CVE-2021-3636
Published
Jul 30, 2021
Updated
Aug 3, 2024
Vendor
Red Hat
Product
Red Hat OpenShift Container Platform
Classifications
CWE-295, T1557
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 30, 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?

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

  1. Affected versionversion=openshift 4.8

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Red Hat · Red Hat OpenShift Container Platformversion=openshift 4.8

Published CVSS scores

4.6NVDCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
4.6Red HatCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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