palletsprojects flask vulnerabilities

Latest palletsprojects 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-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...

3. CVE-2019-1010083 Pallets Project Flask is vulnerable to Denial of Service via Unexpected memory usage

   Published 2019-07-17

   High·CVSS 7.5 EPSS 1.8%

   The Pallets Project Flask before 1.0 is affected by: unexpected memory usage. The impact is: denial of service. The attack vector is: crafted encoded JSON data. The fixed version is: 1. NOTE: this may overlap CVE-2018-1000656.

4. CVE-2018-1000656 Flask is vulnerable to Denial of Service via incorrect encoding of JSON data

   Published 2018-08-20

   High·CVSS 7.5 EPSS 3.9%

   The Pallets Project flask version Before 0.12.3 contains a CWE-20: Improper Input Validation vulnerability in flask that can result in Large amount of memory usage possibly leading to denial of service. This attack appear to be exploitable via Attacker provides JSON data in incor...

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.