CVE-2021-20323

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

Published: 2022-03-25 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20323 is rated Moderate Risk (53.8/100): CVSS Medium severity, with high exploitation likelihood (EPSS 37.25%, 98th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-20323

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 66.05% 37.25% -28.81%
2 2026-06-08 70.27% 66.05% -4.21%
3 2026-05-27 — 70.27% —

Full EPSS history (57 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20323

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-20323

GitHub Security Advisory for CVE-2021-20323

GHSA-xpgc-j48j-jwv9 · Severity: medium · Ecosystem: maven — Cross-site Scripting in Keycloak

OS Trackers for CVE-2021-20323

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2021-20323

Affected software / configurations for CVE-2021-20323

Vendor Product Version Raw CPE
redhat keycloak < 17.0.0 cpe:2.3:a:redhat:keycloak:*:*:*:*:*:*:*:*

References for CVE-2021-20323

URL Tags
https://bugzilla.redhat.com/show_bug.cgi?id=2013577 Issue Tracking Third Party Advisory
cvelogic Threat Intelligence