What is CVE-2021-3989?

CVE-2021-3989 is a medium-severity vulnerability in Showdoc, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2021-12-01.

How severe is CVE-2021-3989?

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

Is CVE-2021-3989 known to be exploited?

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

Open Redirect in Showdoc

CVE-2021-3989

showdoc is vulnerable to URL Redirection to Untrusted Site

Vulnerability class: Open Redirect

Published 2021-12-01 · 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: 0.008 (54.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: +0.000

Affected products

Showdoc
Star7th Star7th/showdoc — versions unspecified

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

Public proof-of-concept exploits

References

huntr.dev/bounties/ffc61eff-efea-42c5-92c2-e043fdf904d5 (Exploit, Patch, Third Party Advisory)
github.com/star7th/showdoc/commit/335afc7ed6d6627c3d0434aa9acc168c77117614 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3989?: CVE-2021-3989 is a medium-severity vulnerability in Showdoc, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2021-12-01.
How severe is CVE-2021-3989?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2021-3989 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.