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Improper handling of new offline login flow

High
dktapps published GHSA-g2fj-p69p-9chp May 24, 2026

Package

composer pocketmine/pocketmine-mp (Composer)

Affected versions

5.43.0

Patched versions

5.43.1

Description

Summary

Offline players can crash the server, even if offline mode is disabled.

Details

If a player joins without Xbox authentication, the server throws this error:

[Server thread/CRITICAL]: Error: "Typed property pocketmine\network\mcpe\protocol\types\login\AuthenticationInfo::$Certificate must not be accessed before initialization"

The issue happens during the login process before the player is fully rejected.

This happened because the @required annotation was removed from the Certificate field in AuthenticationInfo, without accounting for this change on the PM side. This caused unauthenticated players (who no longer provide the Certificate field) to trigger a server crash due to the field being uninitialized.

PoC

  1. Join using a client without Xbox authentication.
  2. The server throws the error above and may crash.

Impact

Any unauthenticated player can remotely crash.

  • No authentication required
  • Affects public servers
  • Can be abused repeatedly

Patches

The issue was fixed with e4aaef4 and 8c75a1d.

Severity

High

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
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVE ID

No known CVE

Weaknesses

Incomplete List of Disallowed Inputs

The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete. Learn more on MITRE.

Credits