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 stuffPatches
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 stuffif captcha.validate():
... # do stuff
else:
... # abortReferences
Tethik/flask-session-captcha#27
For more information
If you have any questions or comments about this advisory:
References
GuillaumeGomez Analyst
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 returnNoneif 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:
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.
References
Tethik/flask-session-captcha#27
For more information
If you have any questions or comments about this advisory:
References