ALAS2023-2026-1476


Amazon Linux 2023 Security Advisory: ALAS2023-2026-1476
Advisory Released Date: 2026-03-25
Advisory Updated Date: 2026-03-25
Severity: Medium

Issue Overview:

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 caches not to cache the response, as it may contain information specific to a logged in user. This is handled in most cases, but some forms of access such as the Python in operator were overlooked. The severity and risk depend on the application being hosted behind a caching proxy that doesn't ignore responses with cookies, not setting a Cache-Control header to mark pages as private or non-cacheable, and accessing the session in a way that only touches keys without reading values or mutating the session. The issue has been fixed in version 3.1.3. (CVE-2026-27205)


Affected Packages:

python-flask


Issue Correction:
Run dnf update python-flask --releasever 2023.10.20260316 or dnf update --advisory ALAS2023-2026-1476 --releasever 2023.10.20260316 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation

New Packages:
noarch:
    python-flask-doc-1.1.4-5.amzn2023.0.1.noarch
    python3-flask-1.1.4-5.amzn2023.0.1.noarch

src:
    python-flask-1.1.4-5.amzn2023.0.1.src