CVE-2021-20323: A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak.

Q: How do I fix CVE-2021-20323?

keycloak: upgrade to 17.0.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-20323 being exploited?

CVE-2021-20323 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-20323 affect?

CVE-2021-20323 affects keycloak. Severity is medium (CVSS 6.1). A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak.

Q: How urgent is CVE-2021-20323?

Priority 51/100. EPSS top 1%: very likely to be exploited; On your watchlist

This week

MEDIUM 6.1WATCHLISTUPGRADE

CVE-2021-20323 is a medium-severity flaw (CVSS 6.1) affecting keycloak. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak.

Why this priority

EPSS top 1%: very likely to be exploited
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	37.2% (top 1%)
CISA exploited list	No
Weakness	CWE-79
Published	2022-03-25
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-03-25 19:15 UTCPublished CVE record published
2026-06-17 03:33 UTCUpdated Record last modified

redhat keycloak UPGRADE

Affected: < 17.0.0

Fixed in: 17.0.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy keycloak || rpm -q keycloak || keycloak --version

2. UPGRADE to 17.0.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade keycloak

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade keycloak

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Keycloak 10.0.0 - 18.0.0 - Cross-Site Scripting

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-20323?

keycloak: upgrade to 17.0.0. Exact commands for each OS are on this page.

Is CVE-2021-20323 being exploited?

CVE-2021-20323 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-20323 affect?

CVE-2021-20323 affects keycloak. Severity is medium (CVSS 6.1). A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak.

How urgent is CVE-2021-20323?

Priority 51/100. EPSS top 1%: very likely to be exploited; On your watchlist

Software pages

Keycloak vulnerabilities

Related CVEs

CVE-2023-6927 MEDIUM 4.6 MITIGATE DOWNGRADE A flaw was found in Keycloak
CVE-2023-6563 HIGH 7.7 UPGRADE DOWNGRADE An unconstrained memory consumption vulnerability was discovered in Keycloak
CVE-2023-6291 HIGH 7.1 UPGRADE DOWNGRADE A flaw was found in the redirect_uri validation logic in Keycloak
CVE-2023-6134 MEDIUM 4.6 UPGRADE UPGRADE A flaw was found in Keycloak that prevents certain schemes in redirects, but permits them if a wildcard is app
CVE-2025-8419 MEDIUM 5.3 MITIGATE A vulnerability was found in Keycloak-services

References

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