CVE-2023-37271
HIGHRestrictedPython vulnerable to arbitrary code execution via stack frame sandbox escape
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
restrictedpython🐍restrictedpython🐍restrictedpythonReal-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
RestrictedPython is a tool that helps to define a subset of the Python language which allows users to provide a program input into a trusted environment. RestrictedPython does not check access to stack frames and their attributes. Stack frames are accessible within at least generators and generator expressions, which are allowed inside RestrictedPython. Prior to versions 6.1 and 5.3, an attacker with access to a RestrictedPython environment can write code that gets the current stack frame in a generator and then walk the stack all the way beyond the RestrictedPython invocation boundary, thus breaking out of the restricted sandbox and potentially allowing arbitrary code execution in the Python interpreter. All RestrictedPython deployments that allow untrusted users to write Python code in the RestrictedPython environment are at risk. In terms of Zope and Plone, this would mean deployments where the administrator allows untrusted users to create and/or edit objects of type Script (Python), DTML Method, DTML Document or Zope Page Template. This is a non-default configuration and likely to be extremely rare. The problem has been fixed in versions 6.1 and 5.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | restrictedpython | all versions | 5.3 |
| 🐍PyPI | restrictedpython | ≥ 6.0a1.dev0&&< 6.1 | 6.1 |
| 🐍PyPI | restrictedpython | all versions | 5.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for restrictedpython. 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 restrictedpython to 5.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-37271 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-2023-37271 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-2023-37271. 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-2023-37271 in your dependencies?
O3 detects CVE-2023-37271 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.