GHSA-7r87-cj48-wj45
Potential Captcha Validate Bypass in flask-session-captcha
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| PyPI | flask-session-captcha | < 1.2.1 | 1.2.1 |
Details
As written in the advisory (Markdown source, shown as plain text).
### 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)
References
External links from the advisory. They lead to third-party sites.
- https://github.com/Tethik/flask-session-captcha/security/advisories/GHSA-7r87-cj48-wj45
- https://nvd.nist.gov/vuln/detail/CVE-2022-24880
- https://github.com/Tethik/flask-session-captcha/pull/27
- https://github.com/Tethik/flask-session-captcha/commit/2811ae23a38d33b620fb7a07de8837c6d65c13e4
- https://github.com/Tethik/flask-session-captcha
- https://github.com/Tethik/flask-session-captcha/releases/tag/v1.2.1
- https://github.com/pypa/advisory-database/tree/main/vulns/flask-session-captcha/PYSEC-2022-193.yaml