pallets flask vulnerabilities

Latest pallets flask CVEs

Newest publication first

1. CVE-2026-27205 Flask session does not add `Vary: Cookie` header when accessed in some ways

   Published 2026-02-21

   Low·CVSS 2.3 EPSS 0.40%

   Flask is a web server gateway interface (WSGI) web application framework. In versions 3.1.2 and below, when the session object is accessed, Flask should set the Vary: Cookie header., resulting in a Use of Cache Containing Sensitive Information vulnerability. The logic instructs c...

2. CVE-2025-47278 Flask uses fallback key instead of current signing key

   Published 2025-05-13

   Low·CVSS 1.8 EPSS 0.19%

   Flask is a web server gateway interface (WSGI) web application framework. In Flask 3.1.0, the way fallback key configuration was handled resulted in the last fallback key being used for signing, rather than the current signing key. Signing is provided by the itsdangerous library....

3. CVE-2023-30861 Flask vulnerable to possible disclosure of permanent session cookie due to missing Vary: Cookie header

   Published 2023-05-02

   High·CVSS 7.5 EPSS 1.3%

   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...

Sources: CVE.org, NVD, CISA KEV, FIRST EPSS, OSV and public exploit-reference metadata. Product matching comes from the published CVE records. A proof-of-concept means public code exists; it is not evidence of exploitation.