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.
// cvss v3.1 vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None
Checked 2026-09-26 at 05:31 UTC. The most recent advisory here was published 2026-09-17. Updated continuously from NVD, GHSA, OSV and CNA feeds.