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CVE-2021-42567

35
FAUCET Score

CVE-2021-42567 is a medium-severity Cross-Site Scripting (XSS) vulnerability affecting Apereo CAS through version 6.4.1, allowing attackers to inject malicious scripts via POST requests to REST API endpoints. This vulnerability has a CVSS score of 6.1, indicating a low attack complexity and requiring user interaction, with potential impacts on confidentiality and integrity. While no active exploitation or Metasploit modules are reported, Nuclei templates exist for detection, and there is minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 6.3.0, < 6.3.7.1CPE matchmatch criteria
cpe:2.3:a:apereo:central_authentication_service:*:*:*:*:*:*:*:*
>= 6.4.0, < 6.4.2CPE matchmatch criteria
cpe:2.3:a:apereo:central_authentication_service:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
8.06%
Probability of exploitation in next 30 days
EPSS Percentile
94.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-42567 · Dec 30, 2021
This CVE's current EPSS score of 0.0806 is in the 98th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

mavenpatch availablevia ghsa
Product: org.apereo.cas:cas-server-core-webFixed in: 6.4.2

Vendor Advisories (1)

mavenGHSA-gfhx-jjwq-63gvmedium

Cross-site Scripting in Apereo CAS

Dec 10, 2021

References

apereo.github.io / 2021/10/18/restvuln
PatchThird Party Advisory
github.com / apereo/cas/releases
Release NotesThird Party Advisory