What is CVE-2021-42654?

CVE-2021-42654 is a critical-severity vulnerability in Sscms Siteserver Cms, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2022-05-24.

How severe is CVE-2021-42654?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Arbitrary file upload in Sscms Siteserver Cms

CVE-2021-42654

SiteServer CMS < V5.1 is affected by an unrestricted upload of a file with dangerous type (getshell), which could be used to execute arbitrary code.

Vulnerability class: Unrestricted File Upload

Published 2022-05-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.017 (76.9th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 76.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: +0.000

Affected products

Sscms Siteserver Cms

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

References

github.com/siteserver/cms (Product, Third Party Advisory)
github.com/siteserver/cms/issues/3236 (Third Party Advisory, Issue Tracking)
github.com/siteserver/cms/releases/download/siteserver-dev-v5.0.92/siteserver_i… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-42654?: CVE-2021-42654 is a critical-severity vulnerability in Sscms Siteserver Cms, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2022-05-24.
How severe is CVE-2021-42654?: Critical severity. CVSS v3 base score is 9.8 out of 10.