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CVE-2021-29621

Observable Response Discrepancy in Flask-AppBuilder

5.3 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

3.40%Down 0.2 points since Jun 8, 2021
90%50%10%1%

What each source reports

CVE List Score used 5.3

Observable Response Discrepancy in 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.

Record
CVE-2021-29621
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
EUVDEUVD-2021-0083 5.3

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.

Record
EUVD-2021-0083
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-03
GitHub AdvisoriesGHSA-434h-p4gx-jm89 6.9

Observable Response Discrepancy in Flask-AppBuilder

Impact

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.

Patches

Upgrade to 3.3.0

For more information

If you have any questions or comments about this advisory:

Record
GHSA-434h-p4gx-jm89
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
NVD 5.3

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.

Record
CVE-2021-29621
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:P/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
OSV 5.3

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.

Record
CVE-2021-29621
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVGHSA-434h-p4gx-jm89 6.9

Observable Response Discrepancy in Flask-AppBuilder

Impact

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.

Patches

Upgrade to 3.3.0

For more information

If you have any questions or comments about this advisory:

Record
GHSA-434h-p4gx-jm89
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
OSVBIT-airflow-2021-29621 No score

Observable Response Discrepancy in 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.

Record
BIT-airflow-2021-29621
Updated
2026-11-02
OSVPYSEC-2021-90 No score

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.

Record
PYSEC-2021-90
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
flask-appbuilder
PyPI
 before 3.3.0
3.3.0
airflow
Bitnami
 1.10.0 up to 1.10.1
1.10.1
flask-appbuilder
PyPI
 before 3.3.0, plus listed versions
0.1.100.1.110.1.120.1.130.1.14
Show 45 moreShow less
0.1.150.1.160.1.170.1.180.1.190.1.200.1.210.1.220.1.230.1.240.1.250.1.260.1.270.1.280.1.290.1.30.1.330.1.340.1.350.1.360.1.370.1.380.1.40.1.430.1.440.1.450.1.460.1.470.1.50.1.60.1.70.1.80.1.90.10.00.10.10.10.20.10.30.10.40.10.50.10.60.10.70.2.00.2.10.2.20.3.0
3.3.0

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-29621 is a medium vulnerability (CVSS 5.3) in Dpgaspar Flask-appbuilder, published May 27, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.40%, the 88th percentile. Fixed in flask-appbuilder 3.3.0.

References

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