CVE-2021-41265: Flask AppBuilder Improper Authentication Vulnerability

HIGH
Advisory Identifier: GHSA-m3rf-7m4w-r66q
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CVSS 8.1
CWE-287
Published
Advisory Summary

CVE-2021-41265 is a HIGH (CVSS 8.1) improper authentication vulnerability (CWE-287: Improper Authentication) affecting Flask AppBuilder libraries in the PyPI ecosystem. The issue involves improper authentication in flask-appbuilder. Remediation is available by upgrading affected packages to version 3.3.4.

CVE-2021-41265 at a Glance

CVE Identifier CVE-2021-41265
GHSA Identifier GHSA-m3rf-7m4w-r66q
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-287: Improper Authentication
Affected Product Flask AppBuilder
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 8.1

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-41265

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

Flask-AppBuilder fixed: 3.3.4 
pip install Flask-AppBuilder>=3.3.4
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 Flask-AppBuilder

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-41265, inspect your installed packages using pip:

pip show Flask-AppBuilder

Analyze the terminal output to locate any version of Flask AppBuilder in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.3.4), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Flask AppBuilder, 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 Improper authentication on the REST API. Allows for a malicious actor with a carefully crafted request to successfully authenticate and gain access to existing protected REST API endpoints. Only affects non database authentication types, and new REST API endpoints. ### Patches Upgrade to Flask-AppBuilder 3.3.4 ### For more information If you have any questions or comments about this advisory: * Open an issue in https://github.com/dpgaspar/Flask-AppBuilder

CVE-2021-41265 Affected Flask AppBuilder Versions

1 component(s)
Fixed Versions:
3.3.4
Product / Package Ecosystem Affected Versions Fixed Version
Flask-AppBuilder
pypi/Flask-AppBuilder
PyPI
< 3.3.4
3.3.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/dpgaspar/Flask-AppBuilder/security/advisories/GHSA-m3rf-7m4w-r66q
NVD — CVE-2021-41265 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-41265
Security Fix Commit FIX COMMIT
https://github.com/dpgaspar/Flask-AppBuilder/commit/eba517aab121afa3f3f2edb011ec6bc4efd61fbc
Flask AppBuilder Source Repository REPOSITORY
https://github.com/dpgaspar/Flask-AppBuilder
Flask AppBuilder Release RELEASE
https://github.com/dpgaspar/Flask-AppBuilder/releases/tag/v3.3.4
Flask AppBuilder Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/flask-appbuilder/PYSEC-2021-851.yaml

Frequently Asked Questions

What is CVE-2021-41265?
CVE-2021-41265 is a security vulnerability in Flask AppBuilder involving Improper Authentication in Flask-AppBuilder under CWE-287: Improper Authentication.
Which Flask AppBuilder versions are affected?
Affected versions include releases prior to 3.3.4 across affected packages: Flask-AppBuilder.
What version fixes CVE-2021-41265?
Upgrading to 3.3.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Flask-AppBuilder affected?
Yes, Flask-AppBuilder is affected in releases prior to 3.3.4. Upgrade your dependency to 3.3.4 or later.
What is the CVSS score of CVE-2021-41265?
CVE-2021-41265 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2021-41265?
CVE-2021-41265 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check PyPI dependencies for CVE-2021-41265?
Run the dependency tree command: 'pip show Flask-AppBuilder'. 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-m3rf-7m4w-r66q",
  "modified" : "2025-03-07T19:09:17Z",
  "published" : "2021-12-09T19:09:07Z",
  "aliases" : [ "CVE-2021-41265" ],
  "summary" : "Improper Authentication in Flask-AppBuilder",
  "details" : "### Impact\nImproper authentication on the REST API. Allows for a malicious actor with a carefully crafted request to successfully authenticate and gain access to existing protected REST API endpoints. Only affects non database authentication types, and new REST API endpoints.\n\n### Patches\nUpgrade to Flask-AppBuilder 3.3.4\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in https://github.com/dpgaspar/Flask-AppBuilder",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "Flask-AppBuilder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.3.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/dpgaspar/Flask-AppBuilder/security/advisories/GHSA-m3rf-7m4w-r66q"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-41265"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dpgaspar/Flask-AppBuilder/commit/eba517aab121afa3f3f2edb011ec6bc4efd61fbc"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/dpgaspar/Flask-AppBuilder"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dpgaspar/Flask-AppBuilder/releases/tag/v3.3.4"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/flask-appbuilder/PYSEC-2021-851.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-12-09T18:14:23Z",
    "nvd_published_at" : "2021-12-09T17:15:00Z"
  }
}