CVE-2021-42567
High PUBLISHEDApereo CAS through 6.4.1 allows XSS via POST requests sent to the REST API endpoints.
Not yet in CISA KEV
Recommended Action
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
At a Glance
Apereo CAS through 6.4.1 allows XSS via POST requests sent to the REST API endpoints.
- CVE Published
- Dec 07, 2021
- Exploitation Reported
- Dec 07, 2021
- CVSS
- 6.1 Medium
- EPSS
- —
Affected Versions
| Vendor | Product | Version | Status |
|---|---|---|---|
| n/a |
n/a
|
n/a |
Affected |
CVE References
- GitHub — apereo/cas github.com · CVE Record https://github.com/apereo/cas/releases
- apereo.github.io/2021/10/18/restvuln apereo.github.io · CVE Record https://apereo.github.io/2021/10/18/restvuln/
Recommended Actions
- Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
- Check enrichment artifacts for scanner coverage and available PoCs before rolling remediation validation.
- Use the Pro API to automate enrichment, telemetry, and workflow delivery for VM, SOC, and CTI pipelines.
Known Exploited Vulnerability Sources
Catalogues that list this CVE as a known exploited vulnerability.
Per-source evidence links for KEV attestations are available through the KEVIntel Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| The Shadowserver First | 2021-12-07 21:10 UTC |
Scanner Artifacts
Nuclei and Metasploit references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-42567.yaml | Apr 25, 2025 |
Virtual Patch
Compensating WAF rules to help reduce exposure to this CVE. Rule content and deployable vendor exports are available with KEVIntel Enterprise.
KEVIntel does not currently have a virtual patch for this CVE. When available, KEVIntel virtual patches ship as deployable ModSecurity, Cloudflare, and AWS WAF rules.
Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to KEVIntel Enterprise users via the Pro API.
Learn About Virtual PatchesCVSS Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
AV:N/AC:M/Au:N/C:N/I:P/A:N
Exploitation Status
Exploited in the wild
Recorded 2021-12-07 21:10:49 UTC · The Shadowserver
Proof of concept available
Recorded 2026-06-12 14:20:25 UTC · Nuclei Templates
Weaknesses (CWE)
-
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Scanner Integrations
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-42567.yaml | Apr 25, 2025 |
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
nuclei · Created Unknown
Timeline
Key exploitation, disclosure, scanner coverage, and KEV attestation events for this CVE.
-
14:20 UTC 30 days ago14:20 UTC · 30 days ago
Public PoC available
Public proof-of-concept code published
-
00:00 UTC about 1 year ago00:00 UTC · about 1 year ago
Nuclei template available
Scanner coverage available
-
21:10 UTC over 4 years ago21:10 UTC · over 4 years ago
Added to KEVIntel KEV Feed
High-confidence, third-party attested exploitation
-
21:10 UTC over 4 years ago21:10 UTC · over 4 years ago
CVE published
Vulnerability disclosed publicly
-
00:00 UTC over 4 years ago00:00 UTC · over 4 years ago
CVE ID reserved
Identifier reserved by the CNA
Automate This Intelligence with the Pro API
Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
Pro API Example
GET /api/v2/pro/kevs/CVE-2021-42567
{
"cve_id": "CVE-2021-42567",
"title": "Apereo CAS through 6.4.1 allows XSS via POST requests sent to the REST API en...",
"affected_vendor": "Apereo",
"affected_product": "CAS",
"affected_versions": [
{ "vendor": "...", "product": "...", "status": "affected", "display_label": "..." }
],
"confidence": "High",
"cvss_score": 6.1,
"epss_score": null,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "...": "Pro API fields" },
"proof_of_concepts": [ "..." ],
"scanner_integrations": [ "..." ]
}