🛡️ AZL-43798 — python-flask

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

CVE-2023-30861 affecting package python-flask 1.1.1-4

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 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 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. This issue has been fixed in versions 2.3.2 and 2.2.5.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.

Affected software

AZL-43798 is recorded against 1 package.

  • python-flask

Timeline and source

Published on 2 May 2023 and last revised on 21 April 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

nvd.nist.gov (Web)

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2023-05-02
Updated 2026-08-12
Modified 2026-04-21
Fix URL N/A

Affected Packages

Software From version Fixed in
python-flask — —

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