CVE-2026-33430: Briefcase Windows MSI Installer Privilege Escalation Vulnerability

HIGH
Advisory Identifier: GHSA-r3r2-35v9-v238
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CVSS 7.3
CWE-732
Published
Advisory Summary

CVE-2026-33430 is a HIGH (CVSS 7.3) windows msi installer privilege escalation vulnerability (CWE-732: Incorrect Permission Assignment for Critical Resource) affecting Briefcase libraries in the PyPI ecosystem. The issue involves windows msi installer privilege escalation via insecure directory permissions. Remediation is available by upgrading affected packages to version 0.3.26.

CVE-2026-33430 at a Glance

CVE Identifier CVE-2026-33430
GHSA Identifier GHSA-r3r2-35v9-v238
Severity HIGH
CVSS v3.1 Base Score 7.3
CWE Classification CWE-732: Incorrect Permission Assignment for Critical Resource
Affected Product Briefcase
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-33430

To remediate this vulnerability, upgrade all affected Briefcase dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

briefcase fixed: 0.3.26 
pip install briefcase>=0.3.26
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show briefcase

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-33430, inspect your installed packages using pip:

pip show briefcase

Analyze the terminal output to locate any version of Briefcase in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.3.26), your application is affected.

Note: The pip show briefcase command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-732: Incorrect Permission Assignment for Critical Resource, where the product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors. In Briefcase, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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: * beeware/briefcase-windows-app-template#86 * beeware/briefcase-windows-VisualStudio-template#85 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.

CVE-2026-33430 Affected Briefcase Versions

1 component(s)
Fixed Versions:
0.3.26
Product / Package Ecosystem Affected Versions Fixed Version
briefcase
pypi/briefcase
PyPI
≥ 0.3.0
< 0.3.26
0.3.26

References

GitHub Advisory / Wiki ADVISORY
https://github.com/beeware/briefcase/security/advisories/GHSA-r3r2-35v9-v238
NVD — CVE-2026-33430 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33430
Briefcase Source Repository REPOSITORY
https://github.com/beeware/briefcase/issues/2759
Briefcase Source Repository REPOSITORY
https://github.com/beeware/briefcase-windows-VisualStudio-template/pull/85
Briefcase Source Repository REPOSITORY
https://github.com/beeware/briefcase-windows-app-template/pull/86
Briefcase Source Repository REPOSITORY
https://github.com/beeware/briefcase
Briefcase Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/briefcase/PYSEC-2026-27.yaml

Frequently Asked Questions

What is CVE-2026-33430?
CVE-2026-33430 is a security vulnerability in Briefcase involving Windows MSI Installer Privilege Escalation via Insecure Directory Permissions under CWE-732: Incorrect Permission Assignment for Critical Resource.
Which Briefcase versions are affected?
Affected versions include releases prior to 0.3.26 across affected packages: briefcase.
What version fixes CVE-2026-33430?
Upgrading to 0.3.26 (or the latest patched release for your respective branch) resolves the vulnerability.
Is briefcase affected?
Yes, briefcase is affected in releases prior to 0.3.26. Upgrade your dependency to 0.3.26 or later.
What is the CVSS score of CVE-2026-33430?
CVE-2026-33430 has a CVSS v3.1 base score of 7.3 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-33430?
CVE-2026-33430 is classified under CWE-732: 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.).
How can I check PyPI dependencies for CVE-2026-33430?
Run the dependency tree command: 'pip show briefcase'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r3r2-35v9-v238",
  "modified" : "2026-06-05T14:26:48Z",
  "published" : "2026-03-23T21:40:10Z",
  "aliases" : [ "CVE-2026-33430" ],
  "summary" : "Briefcase: Windows MSI Installer Privilege Escalation via Insecure Directory Permissions ",
  "details" : "### Impact\n\nIf 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.\n\n### Patches\n\nThe problem is caused by the template used to generate the WXS file for Windows projects. It was fixed with the following PRs:\n\n* beeware/briefcase-windows-app-template#86\n* beeware/briefcase-windows-VisualStudio-template#85\n\nThese 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.\n\n### Workarounds\n\nThe 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.\n\n### Resources\n\nbeeware/briefcase#2759 is a formal bug report of the problem.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "briefcase"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.3.0"
      }, {
        "fixed" : "0.3.26"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/beeware/briefcase/security/advisories/GHSA-r3r2-35v9-v238"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33430"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/beeware/briefcase/issues/2759"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/beeware/briefcase-windows-VisualStudio-template/pull/85"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/beeware/briefcase-windows-app-template/pull/86"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/beeware/briefcase"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/briefcase/PYSEC-2026-27.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-732" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-23T21:40:10Z",
    "nvd_published_at" : "2026-03-26T17:16:38Z"
  }
}