GHSA-xp4f-g2cm-rhg7 CVE-2026-86200
PocketMine-MP has LogDoS by many junk properties in client data JWT in LoginPacket
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.64%
- Chance of exploitation in the next 30 days. Higher than 50.56% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-779 Logging of Excessive Data
- Fix
5.42.1- Upgrade pocketmine/pocketmine-mp to this version or later
Description
Impact
Attackers can fill the body of the clientData JWT in LoginPacket with lots of junk properties, causing the server to flood warning messages, as well as wasting CPU time.
This happens because the JsonMapper instance used to process the JWT body is configured to warn on unexpected properties instead of rejecting them outright. While this behaviour increases flexibility for random changes introduced by Microsoft, it also creates vulnerabilities if not handled carefully.
This vulnerability affects PocketMine-MP servers exposed to a public network where unknown actors may have access.
Patches
This issue was fixed in c1d4a813fb8c21bfd8b9affd040da864b794df71 by restricting the number of unknown properties to 10, and rejecting the packet if this limit is exceeded. This continues to tolerate random additions to the JWT between versions, while preventing the logger from being abused by clients to slow down the server.
Workarounds
Plugins can handle DataPacketReceiveEvent to capture LoginPacket, and pre-process the clientData JWT to ensure it doesn't have any unusual properties in it. This can be achieved using JsonMapper (see the original affected code below) and setting the bExceptionOnUndefinedProperty flag to true. A JsonMapper_Exception will be thrown if the JWT is problematic.
However, it's important to caveat that this approach may cause login failures if any unexpected properties appear out of the blue in future versions (which has happened in the past).
References
Affected code:
https://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L289-L303 https://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L334-L350
Affected versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| pocketmine/pocketmine-mp | < 5.42.1 |
5.42.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
pocketmine/pocketmine-mp Packagist → 5.42.1
- composer
composer require pocketmine/pocketmine-mp:^5.42.1
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- Low
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Weakness
CWE-779: Logging of Excessive Data
The product logs too much information, making log files hard to process and possibly hindering recovery efforts or forensic analysis after an attack.
How to prevent it
- Architecture and Design: Suppress large numbers of duplicate log messages and replace them with periodic summaries. For example, syslog may include an entry that states "last message repeated X times" when recording repeated events.
- Architecture and Design: Support a maximum size for the log file that can be controlled by the administrator. If the maximum size is reached, the admin should be notified. Also, consider reducing functionality of the product. This may result in a denial-of-service to legitimate product users, but it will prevent the product from adversely impacting the entire system.
- Implementation: Adjust configurations appropriately when the product is transitioned from a debug state to production.
References
Packages
Other links
- github.com/pmmp/PocketMine-MP/security/advisories/GHSA-xp4f-g2cm-rhg7
- github.com/pmmp/PocketMine-MP/commit/c1d4a813fb8c21bfd8b9affd040da864b794df71
- github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketH…
- github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketH…
- vulncheck.com/advisories/pocketmine-mp-before-5.42.1-logdos-via-loginpacket-client…
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-pg53-p7qp-65cv PocketMine-MP has potential memory/network vulnerability from repeated ResourcePackClientResponsePacket packets | Low | Also affects pocketmine/pocketmine-mp |
| GHSA-f9jp-856v-8642 PocketMine-MP: Player entities can still die and drop items in flaggedForDespawn state | Medium | Also affects pocketmine/pocketmine-mp |
| GHSA-7hmv-4j2j-pp6f PocketMine-MP: Network amplification vulnerability with `ActorEventPacket` | Medium | Also affects pocketmine/pocketmine-mp |
| GHSA-788v-5pfp-93ff PocketMine-MP: JSON decoding of unlimited size large arrays/objects in ModalFormResponse Handling | Medium | Also affects pocketmine/pocketmine-mp |
| GHSA-h6rj-3m53-887h PocketMine-MP: LogDoS by large complex unknown property logging in clientData in LoginPacket | High | Also affects pocketmine/pocketmine-mp |
| GHSA-fqqv-56h5-f57g PocketMine-MP `ResourcePackDataInfoPacket` amplification vulnerability due to lack of resource pack sequence status checking | Medium | Also affects pocketmine/pocketmine-mp |
| GHSA-g274-c6jj-h78p PocketMine-MP allows malicious client data to waste server resources due to lack of limits for explode() | Medium | Also affects pocketmine/pocketmine-mp |
| GHSA-h6j3-j35f-v2x7 PocketMine-MP server crash with certain invalid JSON payloads in `LoginPacket` due to dependency vulnerability (3rd time) | High | Also affects pocketmine/pocketmine-mp |
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