What is CVE-2023-3521?

CVE-2023-3521 is a medium-severity vulnerability in Fossbilling, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2023-07-06.

How severe is CVE-2023-3521?

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

Is CVE-2023-3521 known to be exploited?

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

XSS in Fossbilling

CVE-2023-3521

Cross-site Scripting (XSS) - Reflected in GitHub repository fossbilling/fossbilling prior to 0.5.4.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2023-07-06 · 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: 0.009 (58.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Fossbilling
Fossbilling Fossbilling/fossbilling — versions unspecified

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

20142995/nuclei-templates

References

huntr.dev/bounties/76a3441d-7f75-4a8d-a7a0-95a7f5456eb0 (Exploit, Patch, Third Party Advisory)
github.com/fossbilling/fossbilling/commit/5eb516d4ebcb764db1b2edf9c8d0539e76ebd… (Patch)

Frequently asked questions

What is CVE-2023-3521?: CVE-2023-3521 is a medium-severity vulnerability in Fossbilling, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2023-07-06.
How severe is CVE-2023-3521?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2023-3521 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.