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TI-2023-14640 Aliases CVE-2023-30861GHSA-m2qf-hxjv-5gpq

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

Priority LOW 35CWE-539Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · None · None
Fix status
Partial Red Hat: 8 fixed, 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0125 69th percentileScored 2026-11-07
Fix Partial flask (pallets): 2.3.2, 2.2.5Flask (PyPI): 2.3.2, 2.2.5Red Hat: 8 advisoriesRed Hat: 8 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
palletsflask2.3.0 to before 2.3.2; before 2.2.52.3.2, 2.2.5Patch availableCNA
—Flask (PyPI)2.3.0 to before 2.3.22.3.2Patch availableGHSA-m2qf-hxjv-5gpq
—Flask (PyPI)before 2.2.52.2.5Patch availableGHSA-m2qf-hxjv-5gpq
  • flask Vendorpallets Affected 2.3.0 to before 2.3.2; before 2.2.5 Fixed in 2.3.2, 2.2.5 Patch available CNA
  • Flask (PyPI) Vendor— Affected 2.3.0 to before 2.3.2 Fixed in 2.3.2 Patch available GHSA-m2qf-hxjv-5gpq
  • Flask (PyPI) Vendor— Affected before 2.2.5 Fixed in 2.2.5 Patch available GHSA-m2qf-hxjv-5gpq

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:palletsprojects:flask:*:*:*:*:*:*:*:*before 2.2.5; 2.3.0 to before 2.3.2Vulnerablepallets
  • cpe:2.3:a:palletsprojects:flask:*:*:*:*:*:*:*:* Versions before 2.2.5; 2.3.0 to before 2.3.2 Vulnerable ·pallets

Remediation

  • Fix · CNA flask (pallets) Fixed in 2.3.2, 2.2.5
  • Fix · GHSA-m2qf-hxjv-5gpq Flask (PyPI) Fixed in 2.3.2 Advisory →
  • Fix · GHSA-m2qf-hxjv-5gpq Flask (PyPI) Fixed in 2.2.5 Advisory →

Red Hat 8 advisories

  • RHSA-2023:7341 Released 2023-11-30 · Red Hat rating Important
    Red Hat Quay security update
    • Quay v3 quay/quay-rhel8
  • RHSA-2023:3541 Released 2023-06-14 · Red Hat rating Low
    OpenShift Container Platform 4.11.43 packages and security update
    • Ironic content for Red Hat OpenShift Container Platform 4.11 python-flask-1:1.1.2-6.el8, python-flask-doc-1:1.1.2-6.el8, python3-flask-1:1.1.2-6.el8
    • Red Hat OpenShift Container Platform 4.11 cri-o-1.24.5-5.rhaos4.11.git8bf967b.el8
  • RHSA-2023:3545 Released 2023-06-14 · Red Hat rating Important
    OpenShift Container Platform 4.12.21 packages and security update
    • Ironic content for Red Hat OpenShift Container Platform 4.12 python-flask-1:2.0.1-3.el9, python-flask-doc-1:2.0.1-3.el9, python3-flask-1:2.0.1-3.el9
    • Red Hat OpenShift Container Platform 4.12 podman-3:4.2.0-4.1.rhaos4.12.el8, podman-catatonit-3:4.2.0-4.1.rhaos4.12.el8, podman-docker-3:4.2.0-4.1.rhaos4.12.el8 +4
Show 5 more Red Hat advisories
  • RHSA-2023:3536 Released 2023-06-13 · Red Hat rating Important
    OpenShift Container Platform 4.13.3 packages and security update
    • Ironic content for Red Hat OpenShift Container Platform 4.13 python-flask-2:2.0.1-4.el9.2, python-flask-doc-2:2.0.1-4.el9.2, python3-flask-2:2.0.1-4.el9.2
    • Red Hat OpenShift Container Platform 4.13 NetworkManager-1:1.42.2-2.el9_2, NetworkManager-adsl-1:1.42.2-2.el9_2, NetworkManager-bluetooth-1:1.42.2-2.el9_2 +28
  • RHSA-2023:3525 Released 2023-06-07 · Red Hat rating Important
    python-flask security update
    • Red Hat Enterprise Linux 7 Extras python-flask-1:0.10.1-7.el7_9
  • RHSA-2023:3440 Released 2023-06-05 · Red Hat rating Important
    Red Hat OpenStack Platform 17.0 (python-flask) security update
    • Red Hat OpenStack Platform 17.0 python-flask-1:1.1.2-6.el9ost, python3-flask-1:1.1.2-6.el9ost
  • RHSA-2023:3446 Released 2023-06-05 · Red Hat rating Important
    Red Hat OpenStack Platform 16.1 (python-flask) security update
    • Red Hat OpenStack Platform 16.1 python-flask-1:1.0.2-8.el8ost, python3-flask-1:1.0.2-8.el8ost
  • RHSA-2023:3444 Released 2023-06-05 · Red Hat rating Important
    Red Hat OpenStack Platform 16.2 (python-flask) security update
    • Red Hat OpenStack Platform 16.2 python-flask-1:1.0.2-8.el8ost, python3-flask-1:1.0.2-8.el8ost

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Ceph Storage 3AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 8AffectedNo fix yet
Red Hat Storage 3AffectedNo fix yet
Ironic content for Red Hat OpenShift Container Platform 4.11Fixed RHSA-2023:3541
Ironic content for Red Hat OpenShift Container Platform 4.12Fixed RHSA-2023:3545
Ironic content for Red Hat OpenShift Container Platform 4.13Fixed RHSA-2023:3536
Quay v3Fixed RHSA-2023:7341
Red Hat Enterprise Linux 7 ExtrasFixed RHSA-2023:3525
Red Hat OpenStack Platform 16.1Fixed RHSA-2023:3446
Red Hat OpenStack Platform 16.2Fixed RHSA-2023:3444
Red Hat OpenStack Platform 17.0Fixed RHSA-2023:3440
Not affected: 6 products
  • Ironic content for Red Hat OpenShift Container Platform 4.11
  • Quay v3
  • Red Hat Ceph Storage 7
  • Red Hat OpenShift Container Platform 4.11
  • Red Hat OpenShift Container Platform 4.12
  • Red Hat OpenShift Container Platform 4.13

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-30861
  2. 2026-10-03 Alias added: GHSA-m2qf-hxjv-5gpq

References

Patch 2

Advisory 2

Other 8

  • TI-2018-16009 The Pallets Project flask version Before 0.12.3 contains a CWE-20: Improper Input… CVSS 3.0HIGH 7.5
  • TI-2019-15971 Uncontrolled resource consumption in Pallets Project Flask CVSS 3.0HIGH 7.5
  • TI-2026-21640 Flask session does not add `Vary: Cookie` header when accessed in some ways CVSS 4.0LOW 2.3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences