CVE-2023-30861 — Flask is a lightweight WSGI web application framework

Flask is a lightweight WSGI web application framework. When all of the following conditions are met, a response containing data intended for one client may be cached and subsequently sent by the proxy to other clients. If the proxy also caches `Set-Cookie` headers, it may send on

01What is this vulnerability?

Flask is a lightweight WSGI web application framework. When all of the following conditions are met, a response containing data intended for one client may be cached and subsequently sent by the proxy to other clients. If the proxy also caches `Set-Cookie` headers, it may send one client's `session` cookie to other clients. The severity depends on the application's use of the session and the…

02Affected products

Vendor	Product	Versions
pallets	flask	>= 2.3.0, < 2.3.2, < 2.2.5

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-05-02T17:04:22.197Z
• Last modified: 2025-02-13T16:49:37.977Z

09References

• github.com — https://github.com/pallets/flask/security/advisories/GHSA-m2qf-hxjv-5gpq
• github.com — https://github.com/pallets/flask/commit/70f906c51ce49c485f1d355703e9cc3386b1cc2b
• github.com — https://github.com/pallets/flask/commit/afd63b16170b7c047f5758eb910c416511e9c965
• github.com — https://github.com/pallets/flask/releases/tag/2.2.5
• github.com — https://github.com/pallets/flask/releases/tag/2.3.2
• www.debian.org — https://www.debian.org/security/2023/dsa-5442
• security.netapp.com — https://security.netapp.com/advisory/ntap-20230818-0006/
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2023/08/msg00024.html