CVE-2022-24880

Potential Captcha Validate Bypass in flask-session-captcha

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

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

CVE-2022-24880 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

A new version (1.2.1) is available that fixes the issue.

1. What is CVE-2022-24880? CVE-2022-24880 is a medium-severity security vulnerability in flask-session-captcha (pip), affecting versions < 1.2.1. It is fixed in 1.2.1.
2. How severe is CVE-2022-24880? CVE-2022-24880 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of flask-session-captcha are affected by CVE-2022-24880? flask-session-captcha (pip) versions < 1.2.1 is affected.
4. Is there a fix for CVE-2022-24880? Yes. CVE-2022-24880 is fixed in 1.2.1. Upgrade to this version or later.
5. Is CVE-2022-24880 exploitable, and should I be worried? Whether CVE-2022-24880 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2022-24880 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2022-24880? Upgrade flask-session-captcha to 1.2.1 or later.