CVE-2021-21241Network attack vector

Authenticated token exposure via unprotected GET

Published Jan 11, 2021 · Updated Aug 3, 2024

Cross-site request forgery in Flask-Security-Too 3.3.0 through 3.4.4 allows remote attackers to obtain an authenticated user's token via GET requests. Handlers for the /login and /change endpoints return the authenticated user's authentication token even though GET requests carry no CSRF protection. A victim must be authenticated and induced to visit a malicious third-party site; the exposed token can enable account access according to its configured lifetime.

CVSS severity7.4
High
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site request forgery in Flask-Security-Too 3.3.0 through 3.4.4 allows remote attackers to obtain an authenticated user's token via GET requests. Handlers for the /login and /change endpoints return the authenticated user's authentication token even though GET requests carry no CSRF protection. A victim must be authenticated and induced to visit a malicious third-party site; the exposed token can enable account access according to its configured lifetime.

The record

CVE
CVE-2021-21241
Published
Jan 11, 2021
Updated
Aug 3, 2024
Vendor
Flask-Middleware
Product
Flask-Security-Too
Classifications
CWE-352, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.3.0, < 3.4.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Flask-Middleware · Flask-Security-Tooversion=>= 3.3.0, < 3.4.5

Published CVSS scores

7.4GitLab Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
T1539Steal Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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