What is CVE-2021-36440?

CVE-2021-36440 is a critical-severity vulnerability in Showdoc, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2021-09-08.

How severe is CVE-2021-36440?

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

Is CVE-2021-36440 known to be exploited?

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

Arbitrary file upload in Showdoc

CVE-2021-36440

Unrestricted File Upload in ShowDoc v2.9.5 allows remote attackers to execute arbitrary code via the 'file_url' parameter in the component AdminUpdateController.class.php'.

Vulnerability class: Unrestricted File Upload

Published 2021-09-08 · 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: 0.048 (91.6th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 92nd percentile — 91.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.048 · newest: 0.048 · change: 0.000

Affected products

Showdoc — versions 2.9.5

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

Public proof-of-concept exploits

References

github.com/star7th/showdoc/issues/1406 (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-36440?: CVE-2021-36440 is a critical-severity vulnerability in Showdoc, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2021-09-08.
How severe is CVE-2021-36440?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-36440 known to be exploited?: 10 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.