CVE-2021-3989 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in showdoc/showdoc. 1 public exploit reference exists, so weaponization risk is real. A fix is available for showdoc/showdoc — see the affected versions and patch details below.
showdoc is vulnerable to URL Redirection to Untrusted Site
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-3989 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 386,684 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
showdoc/showdocReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
showdoc is vulnerable to URL Redirection to Untrusted Site
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | showdoc/showdoc | all versions | 2.9.13composer require showdoc/showdoc:^2.9.13 |
Affected Products
showdocshowdocResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for showdoc/showdoc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update showdoc/showdoc to 2.9.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3989 is resolved across your whole dependency graph.
Workarounds
Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.
Frequently Asked Questions
Is CVE-2021-3989 in your dependencies?
Find it across Packagist, including transitive dependencies.