Skip to content

Briefcase: Windows MSI Installer Privilege Escalation via Insecure Directory Permissions

High severity GitHub Reviewed Published Mar 20, 2026 in beeware/briefcase • Updated Mar 23, 2026

Package

pip briefcase (pip)

Affected versions

>= 0.3.0, < 0.3.26

Patched versions

0.3.26

Description

Impact

If a developer uses Briefcase to produce an Windows MSI installer for a project, and that project is installed for All Users (i.e., per-machine scope), the installation process creates an directory that inherits all the permissions of the parent directory. Depending on the location chosen by the installing user, this may allow a low privilege but authenticated user to replace or modify the binaries installed by the application. If an administrator then runs the altered binary, the binary will run with elevated privileges.

Patches

The problem is caused by the template used to generate the WXS file for Windows projects. It was fixed with the following PRs:

These patches have been backported to the templates used in Briefcase 0.3.26, 0.4.0, and 0.4.1. Re-running briefcase create on your Briefcase project will result in the updated templates being used.

Workarounds

The change from beeware/briefcase-windows-app-template#86 can be added to any existing Briefcase .wxs file generated by Briefcase 0.3.24 or later.

Resources

beeware/briefcase#2759 is a formal bug report of the problem.

References

@freakboy3742 freakboy3742 published to beeware/briefcase Mar 20, 2026
Published to the GitHub Advisory Database Mar 23, 2026
Reviewed Mar 23, 2026
Last updated Mar 23, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

EPSS score

Weaknesses

Incorrect Permission Assignment for Critical Resource

The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors. Learn more on MITRE.

CVE ID

CVE-2026-33430

GHSA ID

GHSA-r3r2-35v9-v238

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.