What is CVE-2021-4072?

CVE-2021-4072 is a medium-severity vulnerability in Elgg, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-12-24.

How severe is CVE-2021-4072?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Elgg

CVE-2021-4072

elgg is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-12-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Elgg
Elgg Elgg/elgg — versions unspecified

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

huntr.dev/bounties/74034253-732a-4251-a0f9-eca5f576c955 (Exploit, Patch, Third Party Advisory, Issue Tracking)
github.com/elgg/elgg/commit/c30b17bf75256ed3fcc84e2083147cc3951423d0 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-4072?: CVE-2021-4072 is a medium-severity vulnerability in Elgg, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-12-24.
How severe is CVE-2021-4072?: Medium severity. CVSS v3 base score is 5.4 out of 10.