Zope AccessControl vulnerable to information disclosure through Python string `format` and `format_map` functions
Impact
Python's string format functionality allows someone controlling the format string to "read" objects accessible (recursively) via attribute access and subscription from accessible objects. Those attribute accesses and subscriptions use Python's full blown getattr and getitem, not the policy restricted AccessControl variants _getattr_ and _getitem_. This can lead to critical information disclosure.
The AccessControl package already guards against direct access to the formatting functions on string instances, but these mitigations did not cover subclasses of str.
Affected are all users who allow untrusted users to create AccessControl controlled Python code and execute it.
Patches
A fix was published with version 7.4.
Workarounds
There is no workaround.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | accesscontrol | < 7.4 | 7.4 |
References
- https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886
- https://nvd.nist.gov/vuln/detail/CVE-2026-77401
- https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43
- https://github.com/zopefoundation/AccessControl
- https://github.com/zopefoundation/AccessControl/releases/tag/7.4
- https://pypi.org/project/accesscontrol
- https://github.com/advisories/GHSA-pq59-9fq7-m886
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N- Weakness (CWE)
CWE-693- Platform
- Python (PyPI)
- Package
accesscontrol- Disclosed
- 17.09.2026
- Updated
- 11.10.2026 15:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-4022 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-pq59-9fq7-m886 - CC BY 4.0
Vulnerability history: accesscontrol
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 07.2021 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 1
- Medium 3
Disclosures per year
- 2021: 2
- 2022: 0
- 2023: 1
- 2024: 1
- 2025: 0
- 2026: 1
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Zope AccessControl vulnerable to information disclosure through Python string `format` and `format_map` functions this entry
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