GHSA-8vfw-v2jv-9hwc: Flow server Cross-Site Scripting Vulnerability

LOW
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CVSS 2.5
CWE-172
Published
Advisory Summary

GHSA-8vfw-v2jv-9hwc is a LOW (CVSS 2.5) cross-site scripting vulnerability (CWE-172: Encoding Error) affecting Flow server libraries in the Maven ecosystem. The issue involves reflected cross-site scripting in development mode handler in vaadin. Remediation is available by upgrading affected packages to version 2.6.2, 6.0.10.

GHSA-8vfw-v2jv-9hwc at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-8vfw-v2jv-9hwc
Severity LOW
CVSS v3.1 Base Score 2.5
CWE Classification CWE-172: Encoding Error
Affected Product Flow server
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 2.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N).

Attack Vector Local (AV:L)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix GHSA-8vfw-v2jv-9hwc

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: 2.6.2 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>2.6.2</version>
</dependency>
com.vaadin:flow-server fixed: 6.0.10 
<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>flow-server</artifactId>
    <version>6.0.10</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 GHSA-8vfw-v2jv-9hwc, 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 2.6.2), 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-172: Encoding Error, where the product does not properly encode or decode the data, resulting in unexpected values. 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

URL encoding error in development mode handler in `com.vaadin:flow-server` versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser. - https://vaadin.com/security/cve-2021-33604

GHSA-8vfw-v2jv-9hwc Affected Flow server Versions

2 component(s)
Fixed Versions:
2.6.26.0.10
Product / Package Ecosystem Affected Versions Fixed Version
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
≥ 2.0.0
< 2.6.2
2.6.2
com.vaadin:flow-server
maven/com.vaadin/flow-server
Maven
≥ 3.0.0
< 6.0.10
6.0.10

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vaadin/flow/security/advisories/GHSA-8vfw-v2jv-9hwc
Flow server Security Information SECURITY
https://vaadin.com/security/cve-2021-33604

Frequently Asked Questions

What is GHSA-8vfw-v2jv-9hwc?
GHSA-8vfw-v2jv-9hwc is a security vulnerability in Flow server involving Reflected cross-site scripting in development mode handler in Vaadin under CWE-172: Encoding Error.
Which Flow server versions are affected?
Affected versions include releases prior to 2.6.2, 6.0.10 across affected packages: com.vaadin:flow-server.
What version fixes GHSA-8vfw-v2jv-9hwc?
Upgrading to 2.6.2, 6.0.10 (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 2.6.2, 6.0.10. Upgrade your dependency to 2.6.2, 6.0.10 or later.
What is the CVSS score of GHSA-8vfw-v2jv-9hwc?
GHSA-8vfw-v2jv-9hwc has a CVSS v3.1 base score of 2.5 (LOW) with vector string CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N.
What CWE is associated with GHSA-8vfw-v2jv-9hwc?
GHSA-8vfw-v2jv-9hwc is classified under CWE-172: Encoding Error (The product does not properly encode or decode the data, resulting in unexpected values.).
How can I check Maven dependencies for GHSA-8vfw-v2jv-9hwc?
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-8vfw-v2jv-9hwc",
  "modified" : "2021-06-24T19:39:30Z",
  "published" : "2021-06-28T16:52:45Z",
  "aliases" : [ ],
  "summary" : "Reflected cross-site scripting in development mode handler in Vaadin",
  "details" : "URL encoding error in development mode handler in `com.vaadin:flow-server` versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser.\n\n- https://vaadin.com/security/cve-2021-33604",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.6.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.6.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.vaadin:flow-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "6.0.10"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.0.9"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vaadin/flow/security/advisories/GHSA-8vfw-v2jv-9hwc"
  }, {
    "type" : "WEB",
    "url" : "https://vaadin.com/security/cve-2021-33604"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-172" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-06-24T19:39:30Z",
    "nvd_published_at" : null
  }
}