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CVE-2021-29621

21
FAUCET Score

CVE-2021-29621 is a user enumeration vulnerability in Flask-AppBuilder versions 3.2.3 and earlier, affecting products like Apache Airflow. An unauthenticated attacker can determine valid usernames by observing differences in server response times during login attempts. This vulnerability has a CVSS score of 5.3 (Medium), indicating a low attack complexity and no user interaction required, with a potential impact of information disclosure. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 3.2.3CPE matchmatch criteria
cpe:2.3:a:dpgaspar:flask-appbuilder:*:*:*:*:*:*:*:*
1.10.0CPE matchmatch criteria
cpe:2.3:a:apache:airflow:1.10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.40%
Probability of exploitation in next 30 days
EPSS Percentile
87.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0340 is in the 83rd percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: Flask-AppBuilderFixed in: 3.3.0

Vendor Advisories (1)

pipGHSA-434h-p4gx-jm89medium

Observable Response Discrepancy in Flask-AppBuilder

May 27, 2021

References

github.com / dpgaspar/Flask-AppBuilder/commit/780bd0e8fbf2d36ada52edb769477e0a4edae580
PatchThird Party Advisory
github.com / dpgaspar/Flask-AppBuilder/security/advisories/GHSA-434h-p4gx-jm89
Third Party Advisory
lists.apache.org / thread.html/r466759f377651f0a690475d5a52564d0e786e82c08d5a5730a4f8352%40%3Cannounce.apache.org%3E
lists.apache.org / thread.html/r5b754118ba4e996adf03863705d34168bffec202da5c6bdc9bf3add5%40%3Cannounce.apache.org%3E
lists.apache.org / thread.html/r91067f953906d93aaa1c69fe2b5472754019cc6bd4f1ba81349d62a0%40%3Ccommits.airflow.apache.org%3E
pypi.org / project/Flask-AppBuilder
ProductThird Party Advisory