Zope AccessControl: Information disclosure through Python string `format` and `format_map` functions

published 2026-09-16 53 d ago modified 2026-10-01 38 d ago also GHSA-pq59-9fq7-m886 , PYSEC-2026-4022 , EUVD-2026-80790

cvss: 6.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits: 0; none known

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.

Patch / fix

fixed in 1 links 2

pypi accesscontrol 7.4

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 53 d ago (2026-09-16)

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
GitHub	3.1	6.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
OSV	3.1	6.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
pypi	accesscontrol	<7.4	7.4

Affected products

zopefoundation AccessControl

Classification

Weakness

CWE-693 Protection Mechanism Failure

References

Sources

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.

Summary