How severe is CVE-2021-20323?

CVE-2021-20323 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-20323?

CVE-2021-20323 affects the following packages: org.keycloak:keycloak-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-20323?

Update org.keycloak:keycloak-core to 17.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20323 is resolved across your whole dependency graph.

How do I detect CVE-2021-20323 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-20323 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2021-20323 actively exploited in the wild?

Yes. There are 3 known exploit references for CVE-2021-20323, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-20323?

CVE-2021-20323 has an EPSS (Exploit Prediction Scoring System) score of 37.2%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2021-20323?

CVE-2021-20323 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for CVE-2021-20323?

A Nuclei detection template exists for CVE-2021-20323, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-20323 published, and has it been updated?

CVE-2021-20323 was published on March 25, 2022 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2021-20323 — keycloak-core

MEDIUM

CVE-2021-20323 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.keycloak:keycloak-core. 3 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for org.keycloak:keycloak-core — see the affected versions and patch details below.

Cross-site Scripting in Keycloak

Also known asGHSA-xpgc-j48j-jwv9

Published

Mar 25, 2022

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

3 known

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

37.2%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

☕org.keycloak:keycloak-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak version 15. The issue was fixed in version 17.0.0.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.keycloak:keycloak-core`	≥ 15.0.0&&< 17.0.0	17.0.0`org.keycloak:keycloak-core:17.0.0`

Affected Products

1 product · 1 configurations

Application

keycloakredhat

< 17.0.0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

A POST based reflected Cross Site Scripting vulnerability on has been id…

github.comGithubDec 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.keycloak:keycloak-core to 17.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20323 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

How to detect CVE-2021-20323

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-20323 -u https://target

Template: Keycloak 10.0.0 - 18.0.0 - Cross-Site Scripting
Severity: medium
Impact: Successful exploitation of this vulnerability could allow an attacker to execute arbitrary JavaScript code in the context of the victim's browser, leading to session hijacking, defacement, or theft of sensitive information.
Remediation: Upgrade Keycloak to a version that is not affected by the vulnerability (10.0.1 or higher).

Template by ProjectDiscovery nuclei-templates (ndmalc, incogbyte), MIT licensed. View the full template. Scan only systems you are authorised to test.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

RHSA-2022:0407RHSSO 7.5.1

Frequently Asked Questions

A POST based reflected Cross Site Scripting vulnerability on has been identified in Keycloak version 15. The issue was fixed in version 17.0.0.

O3 Security · Impact-Aware SCA

Is CVE-2021-20323 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

OpenSSF Scorecard

Package health score

keycloak

9.3/10

Code-Review10/10

Maintained10/10

Branch-Protection8/10

Assessed Nov 2, 2026

Timeline

Disclosed

Mar 25, 2022

First exploit

Dec 7, 2022

Last updated

Oct 24, 2026

Identifiers

CVE-2021-20323

GHSA-xpgc-j48j-jwv9

References

Advisorynvd.nist.gov · CVE 2021 20323 Reportbugzilla.redhat.com · show bug.cgi Packagegithub.com · keycloak

Related vulnerabilities

This CVE is medium severity; 7 of 8 other CVEs affecting keycloak-core are rated as high or higher (top: high).

CVE-2024-4028CVE-2024-10039CVE-2024-7318CVE-2023-6841CVE-2024-7260CVE-2023-6927CVE-2023-4918CVE-2023-0105

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026