What is CVE-2018-18840?

CVE-2018-18840 is a medium-severity vulnerability in Sem-Cms Semcms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2018-10-30.

How severe is CVE-2018-18840?

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

XSS in Sem-Cms Semcms

CVE-2018-18840

XSS was discovered in SEMCMS PHP V3.4 via the SEMCMS_SeoAndTag.php?Class=edit&CF=SeoAndTag tag_indexmetatit parameter.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2018-10-30 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.006 (44.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Sem-Cms Semcms — versions 3.4

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/m3lon/XSS-Expoit/blob/master/SEMCMS Stored XSS Vulnerability.md (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2018-18840?: CVE-2018-18840 is a medium-severity vulnerability in Sem-Cms Semcms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2018-10-30.
How severe is CVE-2018-18840?: Medium severity. CVSS v3 base score is 5.4 out of 10.