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CVE-2021-23385

21
FAUCET Score

CVE-2021-23385 is an open redirect vulnerability affecting all versions of the unmaintained Flask-Security package. It allows an attacker to bypass URL validation in the get_post_logout_redirect and get_post_login_redirect functions, redirecting users to arbitrary URLs via specially crafted input like \\\evil.com/path. This vulnerability has a CVSS score of 6.1 (Medium) and is exploitable only when using an alternative WSGI server or modifying Werkzeug's default behavior, requiring user interaction. There is no evidence of active exploitation, public exploit code, or inclusion in the KEV catalog, though it has received some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:flask-security_project:flask-security:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.4MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.91%
Probability of exploitation in next 30 days
EPSS Percentile
56.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0091 is in the 68th percentile among its peer group of 26,221 CVEs.

Social Chatter

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

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

pipGHSA-cg8c-gc2j-2wf7medium

Flask-Security vulnerable to Open Redirect

Oct 7, 2022

References

github.com / mattupstate/flask-security
ProductThird Party Advisory
lists.debian.org / debian-lts-announce/2023/08/msg00034.html
security.snyk.io / vuln/SNYK-PYTHON-FLASKSECURITY-1293234
ExploitThird Party Advisory
snyk.io / blog/url-confusion-vulnerabilities
Technical DescriptionThird Party Advisory