Vulnerabilities in pkg:maven/org.geysermc/connector

PACKAGE
Advisory Identifier: GHSA-h77f-xxx7-4858
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Advisory Summary

CVE-2021-39177 is a HIGH (CVSS 7.4) user impersonation due to incorrect vulnerability (CWE-287: Improper Authentication) affecting Connector libraries in the Maven ecosystem. The issue involves user impersonation due to incorrect handling of the login jwt. Remediation is available by upgrading affected packages to version 1.4.2-SNAPSHOT.

1 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:maven/org.geysermc/connector

1 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:maven/org.geysermc/connector. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-h77f-xxx7-4858 CVE-2021-39177 HIGH User impersonation due to incorrect handling of the login JWT

CVE-2021-39177 at a Glance

CVE Identifier CVE-2021-39177
GHSA Identifier GHSA-h77f-xxx7-4858
Severity HIGH
CVSS v3.1 Base Score 7.4
CWE Classification CWE-287: Improper Authentication
Affected Product Connector
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.4

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

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

How to Fix CVE-2021-39177

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

org.geysermc:connector fixed: 1.4.2-SNAPSHOT 
<dependency>
    <groupId>org.geysermc</groupId>
    <artifactId>connector</artifactId>
    <version>1.4.2-SNAPSHOT</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=org.geysermc

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-39177, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.geysermc

Analyze the terminal output to locate any version of Connector in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.4.2-SNAPSHOT), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.geysermc 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-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Connector, 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

### Impact <!--_What kind of vulnerability is it? Who is impacted?_--> This allows anyone that can connect to the server to forge a LoginPacket with manipulated JWT token allowing impersonation as any Bedrock user. Unless credentials are saved in your configuration, online mode is not affected as users are still required to log in separately. If your credentials are saved, there is no risk of exposing your email or password. ### Patches <!--_Has the problem been patched? What versions should users upgrade to?_--> This was patched as part of https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6 and https://github.com/GeyserMC/Geyser/commit/ab2f5b326fe590e09167e8b45b4b165ac06ecd13. if your Geyser version is `1.4.2-SNAPSHOT` or later, the issue has been addressed on your build. ### Workarounds <!--_Is there a way for users to fix or remediate the vulnerability without upgrading?_--> Geyser strongly recommends updating to fix this issue. If this isn't possible: - Use online mode and don't save credentials in your Geyser configuration - Use an additional authentication method on the Java server ### References <!--_Are there any links users can visit to find out more?_--> This was disclosed to us by a staff member over at Hive; you can read their disclosure here: https://updates.playhive.com/changelog/weekend-maintenance-breakdown ### For more information If you have any questions or comments about this advisory: * Come talk to us over on our [Discord](https://discord.gg/geysermc) server in the [#development](https://discord.com/channels/613163671870242838/613170125696270357) channel

CVE-2021-39177 Affected Connector Versions

1 component(s)
Fixed Versions:
1.4.2-SNAPSHOT
Product / Package Ecosystem Affected Versions Fixed Version
org.geysermc:connector
maven/org.geysermc/connector
Maven
< 1.4.2-SNAPSHOT
1.4.2-SNAPSHOT

References

GitHub Advisory / Wiki ADVISORY
https://github.com/GeyserMC/Geyser/security/advisories/GHSA-h77f-xxx7-4858
NVD — CVE-2021-39177 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-39177
Security Fix Commit FIX COMMIT
https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6
Connector Source Repository REPOSITORY
https://github.com/GeyserMC/Geyser
updates.playhive.com/changelog/weekend-m... WEB
https://updates.playhive.com/changelog/weekend-maintenance-breakdown

Frequently Asked Questions

What is CVE-2021-39177?
CVE-2021-39177 is a security vulnerability in Connector involving User impersonation due to incorrect handling of the login JWT under CWE-287: Improper Authentication.
Which Connector versions are affected?
Affected versions include releases prior to 1.4.2-SNAPSHOT across affected packages: org.geysermc:connector.
What version fixes CVE-2021-39177?
Upgrading to 1.4.2-SNAPSHOT (or the latest patched release for your respective branch) resolves the vulnerability.
Is connector affected?
Yes, org.geysermc:connector is affected in releases prior to 1.4.2-SNAPSHOT. Upgrade your dependency to 1.4.2-SNAPSHOT or later.
What is the CVSS score of CVE-2021-39177?
CVE-2021-39177 has a CVSS v3.1 base score of 7.4 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2021-39177?
CVE-2021-39177 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check Maven dependencies for CVE-2021-39177?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.geysermc'. 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-h77f-xxx7-4858",
  "modified" : "2026-10-01T18:41:47Z",
  "published" : "2021-09-07T23:04:04Z",
  "aliases" : [ "CVE-2021-39177" ],
  "summary" : "User impersonation due to incorrect handling of the login JWT",
  "details" : "### Impact\n<!--_What kind of vulnerability is it? Who is impacted?_-->\nThis allows anyone that can connect to the server to forge a LoginPacket with manipulated JWT token allowing impersonation as any Bedrock user. Unless credentials are saved in your configuration, online mode is not affected as users are still required to log in separately. If your credentials are saved, there is no risk of exposing your email or password.\n\n### Patches\n<!--_Has the problem been patched? What versions should users upgrade to?_-->\nThis was patched as part of https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6 and https://github.com/GeyserMC/Geyser/commit/ab2f5b326fe590e09167e8b45b4b165ac06ecd13. if your Geyser version is `1.4.2-SNAPSHOT` or later, the issue has been addressed on your build.\n\n### Workarounds\n<!--_Is there a way for users to fix or remediate the vulnerability without upgrading?_-->\nGeyser strongly recommends updating to fix this issue. If this isn't possible:\n- Use online mode and don't save credentials in your Geyser configuration\n- Use an additional authentication method on the Java server\n\n### References\n<!--_Are there any links users can visit to find out more?_-->\nThis was disclosed to us by a staff member over at Hive; you can read their disclosure here: https://updates.playhive.com/changelog/weekend-maintenance-breakdown\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Come talk to us over on our [Discord](https://discord.gg/geysermc) server in the [#development](https://discord.com/channels/613163671870242838/613170125696270357) channel",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.geysermc:connector"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.2-SNAPSHOT"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/GeyserMC/Geyser/security/advisories/GHSA-h77f-xxx7-4858"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-39177"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/GeyserMC/Geyser"
  }, {
    "type" : "WEB",
    "url" : "https://updates.playhive.com/changelog/weekend-maintenance-breakdown"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-07T14:04:02Z",
    "nvd_published_at" : "2021-08-30T23:15:00Z"
  }
}