CVE-2022-24880 is a medium-severity (CVSS 5.3) CWE-253 vulnerability in flask-session-captcha. A fix is available for flask-session-captcha — see the affected versions and patch details below.
Potential Captcha Validate Bypass in flask-session-captcha
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2022-24880.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
flask-session-captchaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
flask-session-captcha is a package which allows users to extend Flask by adding an image based captcha stored in a server side session.
The captcha.validate() function would return None if passed no value (e.g. by submitting a request with an empty form).
If implementing users were checking the return value to be False, the captcha verification check could be bypassed.
Sample vulnerable code:
if captcha.validate() == False:
... # abort
else:
... # do stuff
Patches
A new version (1.2.1) is available that fixes the issue.
Workarounds
Users can workaround the issue by not explicitly checking that the value is False.
Checking the return value less explicitly should still work.
if not captcha.validate():
... # abort
else:
... # do stuff
if captcha.validate():
... # do stuff
else:
... # abort
References
https://github.com/Tethik/flask-session-captcha/pull/27
For more information
If you have any questions or comments about this advisory:
- Open an issue in the github repo
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | flask-session-captcha | all versions | 1.2.1pip install --upgrade 'flask-session-captcha==1.2.1' |
Affected Products
flask-session-captchaflask-session-captcha_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flask-session-captcha, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update flask-session-captcha to 1.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-24880 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2022-24880 in your dependencies?
Find it across PyPI, including transitive dependencies.