Cyber Resilience

CVE-2021-40555

MediumPublic PoC

Published: 16 February 2023

Published
16 February 2023
Modified
19 March 2025
KEV Added
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Patch
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CVSS Score v3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0033 56.4th percentile
Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-40555 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Flatcore Flatcore. Its CVSS base score is 5.4 (Medium).

Operationally, ranked in the top 43.6% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

EU & UK References

Vulnerability details

Cross site scripting (XSS) vulnerability in flatCore-CMS 2.2.15 allows attackers to execute arbitrary code via description field on the new page creation form.

CWE(s)
CWE-79

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

flatcore
flatcore
2.0.7

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing
addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

SI-10 Information Input Validation
addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

SI-15 Information Output Filtering
addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

References