> CVE-2026-27205 [LOW]

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PUBLISHED
2026-02-21 06:17
MODIFIED
2026-02-21 06:17
CVSS_SCORE V3
2.3
EPSS (Prob. Exploit)
0.49%
Top 59.2%
DATA SOURCES:
NVD đź”— 2026-02-21 CWE MITRE đź”— 2026-11-01 FIRST EPSS đź”— 2026-10-25 GITHUB đź”— 2026-11-04 OSV đź”— 2026-07-26

> DESCRIPTION

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.

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
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/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:X

> MÉTRIQUES CVSS DÉTAILLÉES

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/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:X
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
Unknown (P)
Interaction inconnue
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
Low (L)
Divulgation limitée d'informations
I (Impact Intégrité)
Integrity Impact
None (N)
Aucune modification de données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
Low
Divulgation limitée d'informations
Intégrité
None
Aucune modification de données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-524

> CWE DETAILED DESCRIPTIONS

CWE-524: Use of Cache Containing Sensitive Information - The code uses a cache that contains sensitive information, but the cache can be read by an actor outside of the intended control sphere.

> GITHUB SECURITY ADVISORY

GHSA-68rp-wp8r-4726 LOW

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

AFFECTED PACKAGES:
PIP / flask
< 3.1.3
Fixed in: 3.1.3

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

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

AFFECTED PACKAGES:
Unknown / Unknown
17 versions affected
ALIASES:
GHSA-68rp-wp8r-4726, PYSEC-2026-2151

> HISTORIQUE DES MODIFICATIONS

Première apparition
21/02/2026 06:17
Source: NVD
📊 ENRICHISSEMENT 01/03/2026 06:46
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-524: Use of Cache Containing Sensitive Information - The code uses a cache that contains sensitive information, but the cache can be read by an actor outside of the intended control sphere.
Total des modifications: 1 Dernière mise à jour: 8 months ago

> REFERENCES

https://github.com/pallets/flask/commit/089cb86dd22bff589a4eafb7ab8e42dc357623b4
https://github.com/pallets/flask/releases/tag/3.1.3
https://github.com/pallets/flask/security/advisories/GHSA-68rp-wp8r-4726
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