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Vulnerabilities

Vulnerability · CVE-2021-29621

Flask-AppBuilder is a development framework, built on top of Flask.

Published Jun 7, 2021 · catalog updated Jun 17, 2026 · Flask-AppBuilder is a development

Last checked Nov 8, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2021-29621. EPSS is 3.40%. Act only if a listed version of Flask-AppBuilder is a development is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Flask-AppBuilder is a development).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
3.40%
Remediation
Version ranges on file
Affected products
cpe apache/airflow · cpe dpgaspar/flask-appbuilder

Flask-AppBuilder is a development framework, built on top of Flask. User enumeration in database authentication in Flask-AppBuilder <= 3.2.3. Allows for a non authenticated user to enumerate existing accounts by timing the response time from the server when you are logging in. Upgrade to version 3.3.0 or higher to resolve.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apache/airflow1.10.0
  • cpe dpgaspar/flask-appbuilder<= 3.2.3

How to fix CVE-2021-29621

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-29621. EPSS is 3.40%. Act only if a listed version of Flask-AppBuilder is a development is installed.

Which versions are affected?

Compare what you have installed with 1.10.0, <= 3.2.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-203: Observable Discrepancy. EPSS 3.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Flask security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 7, 2021 · Monitored products — high

    Detected

    Flask-AppBuilder is a development framework, built on top of Flask. User enumeration in database authentication in Flask-AppBuilder <= 3.2.3. Allows for a non authenticated user to enumerate existing accounts by timing the response time from the server when you are logging in. Upgrade to version 3.3.0 or higher to resolve.

  2. Jun 17, 2026 · Monitored products — high

    Updated

    Flask-AppBuilder is a development framework, built on top of Flask. User enumeration in database authentication in Flask-AppBuilder <= 3.2.3. Allows for a non authenticated user to enumerate existing accounts by timing the response time from the server when you are logging in. Upgrade to version 3.3.0 or higher to resolve.

Sources

  • CVE.orgVulnerability recordCVE-2021-29621

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2021-29621

    Flask-AppBuilder is a development framework, built on top of Flask. User enumeration in database authentication in Flask-AppBuilder <= 3.2.3. Allows for a non authenticated user to enumerate existing accounts by timing the response time from the server when you are logging in. Upgrade to version 3.3.0 or higher to resolve.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 8, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • Monitored products — highNov 2, 2026