Update dependency flask to v3.1.3 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
flask (changelog)	==3.1.2 → ==3.1.3

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Flask session does not add Vary: Cookie header when accessed in some ways

CVE-2026-27205 / GHSA-68rp-wp8r-4726

More information

Details

When the session object is accessed, Flask should set the Vary: Cookie header. This 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 depends on the application's use of the session, and the cache's behavior regarding cookies. The risk depends on all these conditions being met.

1. The application must be hosted behind a caching proxy that does not ignore responses with cookies.
2. The application does not set a Cache-Control header to indicate that a page is private or should not be cached.
3. The application accesses the session in a way that does not access the values, only the keys, and does not mutate the session.

Severity

• CVSS Score: 2.3 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/pallets/flask/security/advisories/GHSA-68rp-wp8r-4726
• https://github.com/pallets/flask/commit/089cb86dd22bff589a4eafb7ab8e42dc357623b4
• https://github.com/pallets/flask/releases/tag/3.1.3
• https://nvd.nist.gov/vuln/detail/CVE-2026-27205
• https://github.com/advisories/GHSA-68rp-wp8r-4726

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

pallets/flask (flask)

v3.1.3

Compare Source

Released 2026-02-18

• The session is marked as accessed for operations that only access the keys
  but not the values, such as in and len. :ghsa:68rp-wp8r-4726

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