CVE-2023-37271 is a high-severity (CVSS 8.4) CWE-913 vulnerability in restrictedpython. A fix is available for restrictedpython — see the affected versions and patch details below.
RestrictedPython vulnerable to arbitrary code execution via stack frame sandbox escape
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-37271.
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.
How urgent is this, really
CVE-2023-37271 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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
Impact
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. 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 scope allowing the call of unrestricted Python code and therefore 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.
Patches
The problem has been fixed in releases 5.3 and 6.1.
Workarounds
There is no workaround available. If you cannot upgrade to the latest release you should ensure the RestrictedPython environment is only available for trusted users.
References
For more information
If you have any questions or comments about this advisory:
- Open an issue in the RestrictedPython issue tracker
- Email us at [email protected]
Credits
Thanks for analysing and reporting the go to:
- Nakul Choudhary (Quasar0147 on GitHub)
- despawningbone on GitHub
- Robert Xiao (nneonneo on GitHub)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | restrictedpython | all versions | 5.3pip install --upgrade 'restrictedpython==5.3' |
| 🐍PyPI | restrictedpython | ≥ 6.0a1.dev0&&< 6.1 | 6.1pip install --upgrade 'restrictedpython==6.1' |
| 🐍PyPI | restrictedpython | all versions | 5.3pip install --upgrade 'restrictedpython==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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-37271 can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2023-37271 in your dependencies?
O3 Security finds CVE-2023-37271 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.