CVE-2021-42567

Apereo CAS through 6.4.1 allows XSS via POST requests sent to the REST API endpoints.

Published: 2021-12-07 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-42567 is rated Moderate Risk (61.2/100): CVSS Medium severity, with high exploitation likelihood (EPSS 48.89%, 98th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +2.62% over the last day, indicating growing attacker interest. 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-2021-42567

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 2026-03-09 46.27% 48.89% +2.62%
2 2026-03-04 35.41% 46.27% +10.86%
3 2026-03-01 — 35.41% —

Full EPSS history (51 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-42567

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-2021-42567

GitHub Security Advisory for CVE-2021-42567

GHSA-gfhx-jjwq-63gv · Severity: medium · Ecosystem: maven — Cross-site Scripting in Apereo CAS

Affected software / configurations for CVE-2021-42567

Vendor Product Version Raw CPE
apereo central_authentication_service >= 6.3.0, < 6.3.7.1 cpe:2.3:a:apereo:central_authentication_service:*:*:*:*:*:*:*:*
apereo central_authentication_service >= 6.4.0, < 6.4.2 cpe:2.3:a:apereo:central_authentication_service:*:*:*:*:*:*:*:*

References for CVE-2021-42567

URL Tags
https://apereo.github.io/2021/10/18/restvuln/ Patch Third Party Advisory
https://github.com/apereo/cas/releases Release Notes Third Party Advisory
cvelogic Threat Intelligence