CVE-2026-2742: Flow server Authentication Bypass Vulnerability

MODERATE
Advisory Identifier: GHSA-rjgh-wgc7-m37j
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CWE-284
Published
Advisory Summary

CVE-2026-2742 is a MODERATE authentication bypass vulnerability (CWE-284: Improper Access Control) affecting Flow server libraries in the Maven ecosystem. The issue involves vaadin vulnerable to authentication bypass when accessing the /vaadin endpoint without a trailing slash. Remediation is available by upgrading affected packages to version 14.14.1, 23.6.7, 24.9.8, 25.0.2.

CVE-2026-2742 at a Glance

CVE Identifier CVE-2026-2742
GHSA Identifier GHSA-rjgh-wgc7-m37j
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-284: Improper Access Control
Affected Product Flow server
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-2742

To remediate this vulnerability, upgrade all affected Flow server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

com.vaadin:flow-server fixed: 14.14.1 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>14.14.1</version>
</dependency>
com.vaadin:flow-server fixed: 23.6.7 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>23.6.7</version>
</dependency>
com.vaadin:flow-server fixed: 24.9.8 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>24.9.8</version>
</dependency>
com.vaadin:flow-server fixed: 25.0.2 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>25.0.2</version>
</dependency>
com.vaadin:vaadin fixed: 25.0.2 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin</artifactId>
    <version>25.0.2</version>
</dependency>
com.vaadin:vaadin fixed: 24.9.8 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin</artifactId>
    <version>24.9.8</version>
</dependency>
com.vaadin:vaadin fixed: 23.6.7 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin</artifactId>
    <version>23.6.7</version>
</dependency>
com.vaadin:vaadin fixed: 14.14.1 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin</artifactId>
    <version>14.14.1</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=com.vaadin

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-2742, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=com.vaadin

Analyze the terminal output to locate any version of Flow server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 14.14.1), your application is affected.

Note: The mvn dependency:tree -Dincludes=com.vaadin command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Flow server, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

An authentication bypass vulnerability exists in Vaadin 14.0.0 through 14.14.0, 23.0.0 through 23.6.6, 24.0.0 through 24.9.7 and 25.0.0 through 25.0.1, applications using Spring Security due to inconsistent path pattern matching of reserved framework paths. Accessing the /VAADIN endpoint without a trailing slash bypasses security filters, and allowing unauthenticated users to trigger framework initialization and create sessions without proper authorization. Users of affected versions using Spring Security should upgrade as follows: 14.0.0-14.14.0 upgrade to 14.14.1, 23.0.0-23.6.6 to 23.6.7, 24.0.0 - 24.9.7 to 24.9.8, and 25.0.0-25.0.1 upgrade to 25.0.2 or newer. Please note that Vaadin versions 10-13 and 15-22 are no longer supported and users should update either to the latest 14, 23, 24, 25 version.

CVE-2026-2742 Affected Flow server Versions

8 component(s)
Fixed Versions:
14.14.123.6.724.9.825.0.2
Product / Package Ecosystem Affected Versions Fixed Version
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
< 14.14.1
14.14.1
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
≥ 23.0.0
< 23.6.7
23.6.7
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
≥ 24.0.0
< 24.9.8
24.9.8
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
≥ 25.0.0
< 25.0.2
25.0.2
com.vaadin:vaadin
maven/com.vaadin/vaadin
Maven
≥ 25.0.0
< 25.0.2
25.0.2
com.vaadin:vaadin
maven/com.vaadin/vaadin
Maven
≥ 24.0.0
< 24.9.8
24.9.8
com.vaadin:vaadin
maven/com.vaadin/vaadin
Maven
≥ 23.0.0
< 23.6.7
23.6.7
com.vaadin:vaadin
maven/com.vaadin/vaadin
Maven
< 14.14.1
14.14.1

References

NVD — CVE-2026-2742 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2742
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/22998
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/23033
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/23034
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/23037
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/23052
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow/pull/23057
Flow server Source Repository REPOSITORY
https://github.com/vaadin/flow
Flow server Security Information SECURITY
https://vaadin.com/security/cve-2026-2742

Frequently Asked Questions

What is CVE-2026-2742?
CVE-2026-2742 is a security vulnerability in Flow server involving Vaadin Vulnerable to Authentication Bypass When Accessing the /VAADIN Endpoint Without a Trailing Slash under CWE-284: Improper Access Control.
Which Flow server versions are affected?
Affected versions include releases prior to 14.14.1, 23.6.7, 24.9.8, 25.0.2 across affected packages: com.vaadin:flow-server, com.vaadin:vaadin.
What version fixes CVE-2026-2742?
Upgrading to 14.14.1, 23.6.7, 24.9.8, 25.0.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is flow-server affected?
Yes, com.vaadin:flow-server is affected in releases prior to 14.14.1, 23.6.7, 24.9.8, 25.0.2. Upgrade your dependency to 14.14.1, 23.6.7, 24.9.8, 25.0.2 or later.
Is vaadin affected?
Yes, com.vaadin:vaadin is affected in releases prior to 25.0.2, 24.9.8, 23.6.7, 14.14.1. Upgrade your dependency to 25.0.2, 24.9.8, 23.6.7, 14.14.1 or later.
What CWE is associated with CVE-2026-2742?
CVE-2026-2742 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check Maven dependencies for CVE-2026-2742?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=com.vaadin'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rjgh-wgc7-m37j",
  "modified" : "2026-03-11T19:00:34Z",
  "published" : "2026-03-10T18:31:21Z",
  "aliases" : [ "CVE-2026-2742" ],
  "summary" : "Vaadin Vulnerable to Authentication Bypass When Accessing the /VAADIN Endpoint Without a Trailing Slash",
  "details" : "An authentication bypass vulnerability exists in Vaadin 14.0.0 through 14.14.0, 23.0.0 through 23.6.6, 24.0.0 through 24.9.7 and 25.0.0 through 25.0.1, applications using Spring Security due to inconsistent path pattern matching of reserved framework paths.\n\nAccessing the /VAADIN endpoint without a trailing slash bypasses security filters, and allowing unauthenticated users to trigger framework initialization and create sessions without proper authorization.\n\nUsers of affected versions using Spring Security should upgrade as follows: 14.0.0-14.14.0 upgrade to 14.14.1, 23.0.0-23.6.6 to 23.6.7, 24.0.0 - 24.9.7 to 24.9.8, and 25.0.0-25.0.1 upgrade to 25.0.2 or newer.\n\nPlease note that Vaadin versions 10-13 and 15-22 are no longer supported and users should update either to the latest 14, 23, 24, 25 version.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/S:N/AU:Y/R:A/V:D/RE:L/U:Amber"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "14.14.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "23.0.0"
      }, {
        "fixed" : "23.6.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "24.0.0"
      }, {
        "fixed" : "24.9.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "25.0.0"
      }, {
        "fixed" : "25.0.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:vaadin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "25.0.0"
      }, {
        "fixed" : "25.0.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:vaadin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "24.0.0"
      }, {
        "fixed" : "24.9.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:vaadin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "23.0.0"
      }, {
        "fixed" : "23.6.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:vaadin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "14.14.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2742"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/22998"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/23033"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/23034"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/23037"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/23052"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/pull/23057"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vaadin/flow"
  }, {
    "type" : "WEB",
    "url" : "https://vaadin.com/security/cve-2026-2742"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T19:00:34Z",
    "nvd_published_at" : "2026-03-10T18:18:49Z"
  }
}