CVE-2023-37271

RestrictedPython vulnerable to arbitrary code execution via stack frame sandbox escape

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

• RestrictedPython security advisory GHSA-wqc8-x2pr-7jqh

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)

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.

CVE-2023-37271 has a CVSS score of 8.4 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.3, 6.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The problem has been fixed in releases 5.3 and 6.1.

1. What is CVE-2023-37271? CVE-2023-37271 is a high-severity security vulnerability in RestrictedPython (pip), affecting versions < 5.3. It is fixed in 5.3, 6.1.
2. How severe is CVE-2023-37271? CVE-2023-37271 has a CVSS score of 8.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2023-37271?
   • RestrictedPython (pip) (versions < 5.3)
   • restrictedpython (pip) (versions >= 0, < 5.3)
4. Is there a fix for CVE-2023-37271? Yes. CVE-2023-37271 is fixed in 5.3, 6.1. Upgrade to this version or later.
5. Is CVE-2023-37271 exploitable, and should I be worried? Whether CVE-2023-37271 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-37271 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-37271?
   • Upgrade RestrictedPython to 5.3 or later
   • Upgrade RestrictedPython to 6.1 or later
   • Upgrade restrictedpython to 5.3 or later

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