GHSA-gxjj-f44v-qm94: Flask Security Too Open Redirect Vulnerability

LOW
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CVSS 3.1
CWE-601
Published
Advisory Summary

GHSA-gxjj-f44v-qm94 is a LOW (CVSS 3.1) open redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Flask Security Too libraries in the PyPI ecosystem. The issue involves open redirect in flask-security-too. Remediation is available in the latest vendor maintenance releases.

GHSA-gxjj-f44v-qm94 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-gxjj-f44v-qm94
Severity LOW
CVSS v3.1 Base Score 3.1
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Flask Security Too
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 3.1

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

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

How to Fix GHSA-gxjj-f44v-qm94

To remediate this vulnerability, upgrade all affected Flask Security Too 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-Security-Too fixed: Latest secure release 
pip install Flask-Security-Too>=Latest secure release
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-Security-Too

How to Check if You Are Affected

To determine whether your Python environment is affected by GHSA-gxjj-f44v-qm94, inspect your installed packages using pip:

pip show Flask-Security-Too

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

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Flask Security Too, 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

# Withdrawn Duplicate of GHSA-6qmf-fj6m-686c # Original description Flask-Security-Too allows redirects after many successful views (e.g. /login) by honoring the ?next query param. There is code in FS to validate that the url specified in the next parameter is either relative OR has the same netloc (network location) as the requesting URL. This check utilizes Pythons urlsplit library. However many browsers are very lenient on the kind of URL they accept and 'fill in the blanks' when presented with a possibly incomplete URL. As a concrete example - setting http://login?next=\\\github.com will pass FS's relative URL check however many browsers will gladly convert this to http://github.com. Thus an attacker could send such a link to an unwitting user, using a legitimate site and have it redirect to whatever site they want. This is considered a low severity due to the fact that if Werkzeug is used (which is very common with Flask applications) as the WSGI layer, it by default ALWAYS ensures that the Location header is absolute - thus making this attack vector mute. It is possible for application writers to modify this default behavior by setting the 'autocorrect_location_header=False`.

GHSA-gxjj-f44v-qm94 Affected Flask Security Too Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
Flask-Security-Too
pypi/Flask-Security-Too
PyPI
≤ 4.0.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/Flask-Middleware/flask-security/security/advisories/GHSA-6qmf-fj6m-686c
NVD — GHSA-gxjj-f44v-qm94 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-32618
Flask Security Too Source Repository REPOSITORY
https://github.com/Flask-Middleware/flask-security/issues/486

Frequently Asked Questions

What is GHSA-gxjj-f44v-qm94?
GHSA-gxjj-f44v-qm94 is a security vulnerability in Flask Security Too involving Open Redirect in Flask-Security-Too under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Flask Security Too versions are affected?
Affected versions include releases prior to current release patches across affected packages: Flask-Security-Too.
What version fixes GHSA-gxjj-f44v-qm94?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is Flask-Security-Too affected?
Yes, Flask-Security-Too is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of GHSA-gxjj-f44v-qm94?
GHSA-gxjj-f44v-qm94 has a CVSS v3.1 base score of 3.1 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N.
What CWE is associated with GHSA-gxjj-f44v-qm94?
GHSA-gxjj-f44v-qm94 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check PyPI dependencies for GHSA-gxjj-f44v-qm94?
Run the dependency tree command: 'pip show Flask-Security-Too'. 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-gxjj-f44v-qm94",
  "modified" : "2021-12-14T18:14:54Z",
  "published" : "2021-12-14T18:14:04Z",
  "withdrawn" : "2021-05-27T19:07:52Z",
  "aliases" : [ ],
  "summary" : "Open Redirect in Flask-Security-Too",
  "details" : "# Withdrawn\n\nDuplicate of GHSA-6qmf-fj6m-686c\n\n# Original description\n\nFlask-Security-Too allows redirects after many successful views (e.g. /login) by honoring the ?next query param. There is code in FS to validate that the url specified in the next parameter is either relative OR has the same netloc (network location) as the requesting URL.\n\nThis check utilizes Pythons urlsplit library. However many browsers are very lenient on the kind of URL they accept and 'fill in the blanks' when presented with a possibly incomplete URL. As a concrete example - setting http://login?next=\\\\\\github.com\nwill pass FS's relative URL check however many browsers will gladly convert this to http://github.com. Thus an attacker could send such a link to an unwitting user, using a legitimate site and have it redirect to whatever site they want.\n\nThis is considered a low severity due to the fact that if Werkzeug is used (which is very common with Flask applications) as the WSGI layer, it by default ALWAYS ensures that the Location header is absolute - thus making this attack vector mute. It is possible for application writers to modify this default behavior by setting the 'autocorrect_location_header=False`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "Flask-Security-Too"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "4.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/Flask-Middleware/flask-security/security/advisories/GHSA-6qmf-fj6m-686c"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-32618"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Flask-Middleware/flask-security/issues/486"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-19T17:52:04Z",
    "nvd_published_at" : null
  }
}