CVE-2020-27838Network attack vector

Client secret disclosure via unauthenticated registration lookup

Published Mar 8, 2021 · Updated Aug 4, 2024

Improper authentication in Red Hat build of Keycloak before 13.0.0 allows remote attackers to read client secrets through registration requests. The client registration endpoint returns stored configuration for a client classified as public without requiring authentication, including a secret retained after its access type changes. Exploitation requires a public client to have been changed to confidential and exposes that client credential without altering server data.

CVSS severity5.3
Medium
EPSS probability17.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Red Hat build of Keycloak before 13.0.0 allows remote attackers to read client secrets through registration requests. The client registration endpoint returns stored configuration for a client classified as public without requiring authentication, including a secret retained after its access type changes. Exploitation requires a public client to have been changed to confidential and exposes that client credential without altering server data.

The record

CVE
CVE-2020-27838
Published
Mar 8, 2021
Updated
Aug 4, 2024
Vendor
Red Hat
Product
Red Hat build of Keycloak
Classifications
CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=keycloak 13.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Red Hat · Red Hat build of Keycloakversion=keycloak 13.0.0

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
5.3Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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