CVE-2026-55830 json
RestrictedPython guard hooks can be shadowed via positional-only arguments
published 2026-07-08 4 mo ago modified 2026-10-25 14 d ago also GHSA-ffg3-p8fm-mjx2 , PYSEC-2026-3917 , EUVD-2026-42434
- cvss
- 8.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 21%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- total
- Assessed
- 4 mo ago
Exploit prediction
0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/zopefoundation/RestrictedPython/security/advisories/GHSA-ffg3-p8fm-mjx2 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.3 | CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L |
| GitHub | 3.1 | 8.3 | CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L |
| OSV | 3.1 | 8.3 | CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | restrictedpython | <8.3 |
8.3 |
Affected products
- zopefoundation RestrictedPython
Classification
- Weakness
-
- CWE-184 Incomplete List of Disallowed Inputs
References
-
github.com
/zopefoundation/RestrictedPython/commit/3737596ec9f28c34a073cc845bd2f4c0a80cb671
web
-
github.com
/zopefoundation/RestrictedPython/security/advisories/GHSA-ffg3-p8fm-mjx2
exploit, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-55830
advisory
-
github.com
/zopefoundation/RestrictedPython
package
-
pypi.org
/project/restrictedpython
package
-
github.com
/advisories/GHSA-ffg3-p8fm-mjx2
advisory
Sources
- CVE List CVE-2026-55830
- GitHub Advisory GHSA-ffg3-p8fm-mjx2
- NVD CVE-2026-55830
- OSV PYSEC-2026-3917
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.