CVE-2026-55830 RestrictedPython guard hooks can be shadowed via positional-only arguments
Attackers can bypass RestrictedPython access policies by shadowing guard hooks using positional-only arguments, potentially escaping the sandbox.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55830?
CVE-2026-55830 is a high-severity vulnerability in zopefoundation RestrictedPython, published on 8 Jul 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
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.
Weakness: CWE-184
Which versions are affected by CVE-2026-55830?
3 open source packages ship an affected version, including restrictedpython and RestrictedPython.
| Package | Affected | Fixed in |
|---|---|---|
restrictedpython PyPI | All versions | 8.3 |
restrictedpython PyPI | All versions | 8.3 |
RestrictedPython PyPI | All versions | 8.3 |
How do I fix CVE-2026-55830?
Upgrade restrictedpython to 8.3 or later.
Is CVE-2026-55830 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55830 exists.
Sources
Also known as CLEANSTART-2026-OY92874, DEBIAN-CVE-2026-55830, ECHO-e362-8d35-27d4, GHSA-ffg3-p8fm-mjx2, MINI-2p37-hfgr-f523, MINI-43g3-7gv6-v29r and 7 more.