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Spring Framework Escalation via Session Fixation in WebFlux

Moderate severity GitHub Reviewed Published Jun 9, 2026 to the GitHub Advisory Database • Updated Jul 30, 2026

Package

maven org.springframework:spring-webflux (Maven)

Affected versions

>= 7.0.0, <= 7.0.7
>= 6.2.0, <= 6.2.18
>= 6.1.0, <= 6.1.21
<= 5.3.39

Patched versions

7.0.8
6.2.19

Description

A WebFlux application with a compromised subdomain (for example, compromised via cross-site scripting (XSS)) is vulnerable to an escalation attack exchanging a known session ID for that of an authenticated user.

Affected versions:
Spring Framework 7.0.0 through 7.0.7; 6.2.0 through 6.2.18; 6.1.0 through 6.1.27; 5.3.0 through 5.3.48.

References

Published by the National Vulnerability Database Jun 9, 2026
Published to the GitHub Advisory Database Jun 9, 2026
Reviewed Jul 30, 2026
Last updated Jul 30, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(12th percentile)

Weaknesses

Session Fixation

Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions. Learn more on MITRE.

CVE ID

CVE-2026-41839

GHSA ID

GHSA-4hfh-6x8g-gwpp

Source code

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