Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M
CVE-2026-55830RestrictedPython guard hooks can be shadowed via positional-only arguments
High 8.3
In plain English
A high-severity security flaw in RestrictedPython from zopefoundation. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
RestrictedPython is a tool that helps to define a subset of the Python language which allows to provide a program input into a trusted environment. Prior to 8.3, check_function_argument_names() rejected protected guard hook names for regular, variadic, and keyword-only arguments but omitted positional-only arguments, allowing __getattr__, _getitem_, _write_, or _print_ to be shadowed by a local parameter and bypass the embedding application's access policy. This issue is fixed in version 8.3.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | restrictedpython | no fix listed | DEBIAN-CVE-2026-55830 |
| Debian:13 | restrictedpython | no fix listed | DEBIAN-CVE-2026-55830 |
| Debian:14 | restrictedpython | 8.4-1 | DEBIAN-CVE-2026-55830 |
| PyPI | restrictedpython | 8.3 | GHSA-ffg3-p8fm-mjx2 |
| PyPI | restrictedpython | 8.3 | PYSEC-2026-3917 |
| Ubuntu:26.04:LTS | restrictedpython | no fix listed | UBUNTU-CVE-2026-55830 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| zopefoundation | RestrictedPython | < 8.3 |
Weakness: CWE-184 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L