Vulnerability · Published Sep 16, 2026 · Assigned by GitHub_M

CVE-2026-77401Zope AccessControl: Information disclosure through Python string `format` and `format_map` functions

Medium 6.8

In plain English

A medium-severity security flaw in AccessControl from zopefoundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.8Medium

Exploit odds (30 days)0.5%top 59.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Zope AccessControl provides a general security framework for use in Zope. Prior to 7.4, applications that allow untrusted users to create and execute AccessControl-controlled Python code do not safely guard str.format and str.format_map when those methods are reached through a str subclass. In both ImplPython.py and cAccessControl.c, Python formatting can recursively access attributes and subscriptions using unrestricted getattr and getitem behavior instead of the policy-restricted getattr and getitem operations. A controlled format string can therefore disclose objects reachable from values available to the formatting operation. This issue is fixed in version 7.4.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	accesscontrol	7.4	GHSA-pq59-9fq7-m886
PyPI	accesscontrol	7.4	PYSEC-2026-4022

Affected products (as reported)

Vendor	Product	Versions
zopefoundation	AccessControl	< 7.4

Weakness: CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

References

https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886 x_refsource_CONFIRM
https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43 x_refsource_MISC
https://github.com/zopefoundation/AccessControl/releases/tag/7.4 x_refsource_MISC