CVE-2021-32807 is a high-severity (CVSS 7.2) CWE-915 vulnerability in accesscontrol. O3 Security confirms whether CVE-2021-32807 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Remote Code Execution via unsafe classes in otherwise permitted modules
Real-World Exposure
accesscontrol🐍accesscontrol🐍zope🐍zopeReal-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
The module AccessControl defines security policies for Python code used in restricted code within Zope applications. Restricted code is any code that resides in Zope's object database, such as the contents of Script (Python) objects. The policies defined in AccessControl severely restrict access to Python modules and only exempt a few that are deemed safe, such as Python's string module. However, full access to the string module also allows access to the class Formatter, which can be overridden and extended within Script (Python) in a way that provides access to other unsafe Python libraries. Those unsafe Python libraries can be used for remote code execution. By default, you need to have the admin-level Zope "Manager" role to add or edit Script (Python) objects through the web. Only sites that allow untrusted users to add/edit these scripts through the web - which would be a very unusual configuration to begin with - are at risk. The problem has been fixed in AccessControl 4.3 and 5.2. Only AccessControl versions 4 and 5 are vulnerable, and only on Python 3, not Python 2.7. As a workaround, a site administrator can restrict adding/editing Script (Python) objects through the web using the standard Zope user/role permission mechanisms. Untrusted users should not be assigned the Zope Manager role and adding/editing these scripts through the web should be restricted to trusted users only. This is the default configuration in Zope.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | accesscontrol | ≥ 4.0&&< 4.3 | 4.3 |
| 🐍PyPI | accesscontrol | ≥ 5.0&&< 5.2 | 5.2 |
| 🐍PyPI | zope | ≥ 4.0&&< 4.3 | 4.3 |
| 🐍PyPI | zope | ≥ 5.0&&< 5.2 | 5.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for accesscontrol. 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 accesscontrol to 4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32807 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-2021-32807 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-2021-32807. 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-2021-32807 in your dependencies?
O3 detects CVE-2021-32807 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.