CVE-2021-21337 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in products-pluggableauthservice. 2 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-21337 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
URL Redirection to Untrusted Site ('Open Redirect') in Products.PluggableAuthService
Real-World Exposure
products-pluggableauthserviceReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Products.PluggableAuthService is a pluggable Zope authentication and authorization framework. In Products.PluggableAuthService before version 2.6.0 there is an open redirect vulnerability. A maliciously crafted link to the login form and login functionality could redirect the browser to a different website. The problem has been fixed in version 2.6.1. Depending on how you have installed Products.PluggableAuthService, you should change the buildout version pin to 2.6.1 and re-run the buildout, or if you used pip simply do `pip install "Products.PluggableAuthService>=2.6.1".
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | products-pluggableauthservice | all versions | 2.6.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Products.PluggableAuthService 2.6.0 - Open Redirect
by Piyush Patil · Jun 2, 2021
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for products-pluggableauthservice. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update products-pluggableauthservice to 2.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21337 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-21337 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-21337. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-21337 in your dependencies?
O3 detects CVE-2021-21337 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.