CVE-2026-27205

mediumpriority · track · 17EPSS 0.004 · 34 %ileDEEUFRUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.40% (34th) EPSS
CVSS 4.3 · medium
Is it mine?
5 products
Check your exposure
Who says so?
7 sources
cnnvd · enisa_euvd · osv · cert_bund

EPSS · scored 2026-10-27

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.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

  • Fixedpython311-Flask-0:2.3.2-150400.3.9.1.noarch as component of SUSE Linux Enterprise Module for Python 3 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-0:2.3.2-150400.3.9.1.noarch as component of openSUSE Leap 15.6suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-doc-0:2.3.2-150400.3.9.1.noarch as component of openSUSE Leap 15.6suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-doc-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-doc-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-doc-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython311-Flask-doc-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-doc-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-doc-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-doc-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython312-Flask-doc-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-doc-0:3.1.3-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-doc-0:3.1.3-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-doc-0:3.1.3-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedpython313-Flask-doc-0:3.1.3-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

02

cvss

Technical severity, 0–10. One row per scoring source.

6.5
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–medium · 0.6–6.5

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 1.4
v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:Nsecondary · OSV
v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:Nsecondary · SUSE Product Security
v4.02.3lowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:Nsecondary · ENISA EU
v4.02.3lowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · security-advisories@github.com
v4.00.6lowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · CVSS-BT (t0sche)
03

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS
04

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-524USCWE-524US
05

affected products (5)

Products and version ranges known to be affected.

06

advisories (6)

Vendor and ecosystem advisories describing this.

  • SUSE-SU-2026:0849-1Security update for python-Flask2026-03-09csaf · suse_csafDE

    Security update for python-Flask

  • WID-SEC-W-2026-2451Oracle Siebel CRM: Mehrere SchwachstellenDeutsch2026-07-21csaf · cert_bundDE

    Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Oracle Siebel CRM ausnutzen, um die Vertraulichkeit, Integrität und Verfügbarkeit zu gefährden.

  • openSUSE-SU-2026:10264-1python311-Flask-3.1.3-1.1 on GA media2026-02-26csaf · suse_csafDE

    python311-Flask-3.1.3-1.1 on GA media

  • GHSA-68rp-wp8r-4726Flask session does not add `Vary: Cookie` header when accessed in some ways2026-02-19ghsa · osvUS

    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.

  • CERTFR-2026-AVI-1378Multiples vulnérabilités dans les produits IBMFrançais2026-10-23vendor · certfrFR
  • PYSEC-2026-21512026-02-21vendor · osvUS

    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.

07

also known as (6)

Other names and identifiers for this entity.

08

sources

Which sources assert this record, and when.

cnnvdenisa_euvdosvcert_bundnvdsuse_csafcertfrNVDCVE.orgMITRE
published 2026-02-21modified 2026-06-17
09

references (10)

External citations — patches, advisories, analysis.

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