What is CVE-2021-4172?

CVE-2021-4172 is a medium-severity vulnerability in Showdoc, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2022-01-22.

How severe is CVE-2021-4172?

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

Is CVE-2021-4172 known to be exploited?

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

XSS in Showdoc

CVE-2021-4172

Cross-site Scripting (XSS) - Stored in GitHub repository star7th/showdoc prior to 2.10.2.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2022-01-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.006 (48.8th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.8% 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

Showdoc
Star7th Star7th/showdoc — versions unspecified

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

References

huntr.dev/bounties/c041b693-877b-4456-b463-19e4c9456eee (Exploit, Patch, Third Party Advisory)
github.com/star7th/showdoc/commit/409c8a1208bbb847046a9496303192980f2e6219 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-4172?: CVE-2021-4172 is a medium-severity vulnerability in Showdoc, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2022-01-22.
How severe is CVE-2021-4172?: Medium severity. CVSS v3 base score is 5.4 out of 10.
Is CVE-2021-4172 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.