# CVE-2023-41039: Sandbox escape via various forms of "format".

Source: https://junglewise.ai/threats/cve-2023-41039-sandbox-escape-via-various-forms-of-format  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-08-30  
License: CC BY 4.0 with a link back

CVE-2023-41039 · Severity: low · CVSS 3.1 · Published 2023-08-30

RestrictedPython is a restricted execution environment for Python to run untrusted code. Python's "format" functionality allows someone controlling the format string to "read" all objects accessible through recursive attribute lookup and subscription from objects he can access. This can lead to critical information disclosure. With `RestrictedPython`, the format functionality is available via the `format` and `format_map` methods of `str` (and `unicode`) (accessed either via the class or its instances) and via `string.Formatter`. All known versions of `RestrictedPython` are vulnerable. This issue has been addressed in commit `4134aedcff1` which has been included in the 5.4 and 6.2 releases. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Technologies: [restrictedpython (PyPI)](https://junglewise.ai/threats/technologies/pypi-restrictedpython). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2023-41039 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-41039 being exploited in the wild.

**How severe is CVE-2023-41039?** Low severity, with a CVSS score of 3.1, published 30 August 2023.

**Which products and versions are affected?** restrictedpython (PyPI) ECOSYSTEM:introduced=0,fixed=5.4, GIT:introduced=0,fixed=4134aedcff17c977da7717693ed89ce56d54c120|ECOSYSTEM:introduced=6.0,fixed=6.2,introduced=0,fixed=5.4.

**Is there a fix for CVE-2023-41039?** Yes. restrictedpython (PyPI): upgrade to 5.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2023-41039?** Check whether you run restrictedpython (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- restrictedpython (PyPI): upgrade to 5.4 or later

  ```sh
  pip install "restrictedpython>=5.4"
  ```


## Affected products

- restrictedpython (PyPI) ECOSYSTEM:introduced=0,fixed=5.4, GIT:introduced=0,fixed=4134aedcff17c977da7717693ed89ce56d54c120|ECOSYSTEM:introduced=6.0,fixed=6.2,introduced=0,fixed=5.4

## Identifiers

- CVE-2023-41039
- GHSA-xjw2-6jm9-rf67
- PYSEC-2023-159

## Related threats

- [RestrictedPython sandbox escape via string.Formatter field resolution](https://junglewise.ai/threats/cve-2026-76825-restrictedpython-sandbox-escape-via-string-formatter-field)
- [Zope RestrictedPython access policy bypass via positional-only arguments](https://junglewise.ai/threats/cve-2026-55830-zope-restrictedpython-access-policy-bypass-via-positional-only)
- [PYSEC-2026-1874 - try/except* clauses could allow bypass RestrictedPython via type confusion bug in the CPython interpreter](https://junglewise.ai/threats/cve-2025-22153-try-except-clauses-could-allow-bypass-restrictedpython-via-type)
- [RestrictedPython information leakage via `AttributeError.obj` and the `string` module](https://junglewise.ai/threats/cve-2024-47532-restrictedpython-information-leakage-via-attributeerror-obj-and)
- [RestrictedPython vulnerable to arbitrary code execution via stack frame sandbox escape](https://junglewise.ai/threats/cve-2023-37271-restrictedpython-vulnerable-to-arbitrary-code-execution-via-stack)