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Security Advisories: GSA_kwCzR0hTQS1tMnFmLWh4anYtNWdwcc4AAzC9

Flask vulnerable to possible disclosure of permanent session cookie due to missing Vary: Cookie header

When all of the following conditions are met, a response containing data intended for one client may be cached and subsequently sent by a 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 proxy'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 strip cookies or ignore responses with cookies.
  2. The application sets session.permanent = True.
  3. The application does not access or modify the session at any point during a request.
  4. SESSION_REFRESH_EACH_REQUEST is enabled (the default).
  5. The application does not set a Cache-Control header to indicate that a page is private or should not be cached.

This happens because vulnerable versions of Flask only set the Vary: Cookie header when the session is accessed or modified, not when it is refreshed (re-sent to update the expiration) without being accessed or modified.

Permalink: https://github.com/advisories/GHSA-m2qf-hxjv-5gpq
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1tMnFmLWh4anYtNWdwcc4AAzC9
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: about 1 year ago
Updated: 6 months ago


CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Identifiers: GHSA-m2qf-hxjv-5gpq, CVE-2023-30861
References: Repository: https://github.com/pallets/flask
Blast Radius: 38.1

Affected Packages

pypi:flask
Dependent packages: 1,970
Dependent repositories: 119,058
Downloads: 88,311,698 last month
Affected Version Ranges: < 2.2.5, >= 2.3.0, < 2.3.2
Fixed in: 2.2.5, 2.3.2
All affected versions: 0.3.1, 0.5.1, 0.5.2, 0.6.1, 0.7.1, 0.7.2, 0.8.1, 0.10.1, 0.11.1, 0.12.1, 0.12.2, 0.12.3, 0.12.4, 0.12.5, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.1.0, 1.1.1, 1.1.2, 1.1.3, 1.1.4, 2.0.0, 2.0.1, 2.0.2, 2.0.3, 2.1.0, 2.1.1, 2.1.2, 2.1.3, 2.2.0, 2.2.1, 2.2.2, 2.2.3, 2.2.4, 2.3.0, 2.3.1
All unaffected versions: 2.2.5, 2.3.2, 2.3.3, 3.0.0, 3.0.1, 3.0.2, 3.0.3