medium5.3

CVE-2022-24880

Potential Captcha Validate Bypass in flask-session-captcha

Impact

### 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: ```python 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. ```python if not captcha.validate(): ... # abort else: ... # do stuff ``` ```python 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](https://github.com/Tethik/flask-session-captcha)

Affected packages

Ecosystem	Package	Affected	Fixed in
pip	`flask-session-captcha`	< 1.2.1	1.2.1

Affected products

Vendor	Product	Affected versions
Flask-Session-Captcha Project	Flask-Session-Captcha	before 1.2.1

Weakness classification

CWE-253 CWE-394 CWE-754