What is CVE-2021-31521?

CVE-2021-31521 is a medium-severity vulnerability in Trend Micro Interscan Web Security Virtual Appliance, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-06-17.

How severe is CVE-2021-31521?

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

XSS in Trend Micro Interscan Web Security Virtual Appliance

CVE-2021-31521

Trend Micro InterScan Web Security Virtual Appliance version 6.5 was found to have a reflected cross-site scripting (XSS) vulnerability in the product's Captive Portal.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-06-17 · 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: 0.014 (71.5th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Trend Micro Interscan Web Security Virtual Appliance — versions 6.5 SP2
Trendmicro Interscan Web Security Virtual Appliance — versions 6.5

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

success.trendmicro.com/solution/000286452 (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-31521?: CVE-2021-31521 is a medium-severity vulnerability in Trend Micro Interscan Web Security Virtual Appliance, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-06-17.
How severe is CVE-2021-31521?: Medium severity. CVSS v3 base score is 5.4 out of 10.