What is CVE-2020-18663?

CVE-2020-18663 is a medium-severity vulnerability in Sir Gnuboard, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-06-24.

How severe is CVE-2020-18663?

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

XSS in Sir Gnuboard

CVE-2020-18663

Cross Site Scripting (XSS) vulnerability in gnuboard5 <=v5.3.2.8 via the act parameter in bbs/move_update.php.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-06-24 · 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: 0.011 (63.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 63rd percentile — 63.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

Sir Gnuboard

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/gnuboard/gnuboard5/issues/43 (Technical Description)
www.seebug.org/vuldb/ssvid-97926 (Technical Description)
github.com/LoRexxar/CVE_Request/tree/master/gnuboard5 mul vuls before v5.3.2.8 (Technical Description, Exploit)

Frequently asked questions

What is CVE-2020-18663?: CVE-2020-18663 is a medium-severity vulnerability in Sir Gnuboard, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-06-24.
How severe is CVE-2020-18663?: Medium severity. CVSS v3 base score is 6.1 out of 10.