What is CVE-2021-33904?

CVE-2021-33904 is a medium-severity vulnerability in Accela Civic Platform, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-06-07.

How severe is CVE-2021-33904?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Is CVE-2021-33904 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XSS in Accela Civic Platform

CVE-2021-33904

In Accela Civic Platform through 21.1, the security/hostSignon.do parameter servProvCode is vulnerable to XSS. NOTE: The vendor states "there are configurable security flags and we are unable to reproduce them with the available information.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-06-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.100 (95.5th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.100 · newest: 0.100 · change: 0.000

Affected products

Accela Civic Platform

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

References

gist.github.com/0xx7/3d934939d7122fe23db11bc48eda9d21 (Third Party Advisory)
packetstormsecurity.com/files/163093/Accela-Civic-Platorm-21.1-Cross-Site-Scrip… (Exploit, VDB Entry, Third Party Advisory)

Frequently asked questions

What is CVE-2021-33904?: CVE-2021-33904 is a medium-severity vulnerability in Accela Civic Platform, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-06-07.
How severe is CVE-2021-33904?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2021-33904 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.