Potential Captcha Validate Bypass in flask-session-captcha

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2022-24880: 1.21% estimated exploitation activity in the next 30 days; percentile 68.36 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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: 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 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

Published by the source

26 Apr 2022, 21:19 UTC

Last modified by the source

21 Feb 2025, 05:28 UTC

Source last checked

26 Oct 2026, 13:17 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7r87-cj48-wj45

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7r87-cj48-wj45

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# Patch Next advisory brief: CVE-2022-24880

Advisory: Potential Captcha Validate Bypass in flask-session-captcha
IDs: CVE-2022-24880, GHSA-7r87-cj48-wj45
Record: https://patchnext.com/advisories/cve-2022-24880 (revision 3, source checked 26 Oct 2026, 13:17 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flask-session-captcha 1.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flask-session-captcha: affected < 1.2.1; fixed in 1.2.1

## Suggested inspection (read-only)
- `python -m pip show flask-session-captcha`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flask-session-captcha.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7r87-cj48-wj45 (OSV record GHSA-7r87-cj48-wj45 lists affected ranges: PyPI flask-session-captcha >=0 <1.2.1 (fixed))
- Verified: https://github.com/advisories/GHSA-7r87-cj48-wj45 (GitHub-reviewed advisory GHSA-7r87-cj48-wj45 lists affected ranges: PyPI flask-session-captcha >=0 <1.2.1)

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