CWE-779
AllowedLogging of Excessive Data
Abstraction: Base · Status: Draft
The product logs too much information, making log files hard to process and possibly hindering recovery efforts or forensic analysis after an attack.
31 vulnerabilities reference this CWE, most recent first.
GHSA-XP4F-G2CM-RHG7
Vulnerability from github – Published: 2026-04-15 19:43 – Updated: 2026-04-15 19:43Impact
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": [
{
"package": {
"ecosystem": "Packagist",
"name": "pocketmine/pocketmine-mp"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.42.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-779"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-15T19:43:33Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Impact\n\nAttackers 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.\n\nThis 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.\n\nThis vulnerability affects PocketMine-MP servers exposed to a public network where unknown actors may have access.\n\n### Patches\n\nThis 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.\n\n### Workarounds\nPlugins can handle `DataPacketReceiveEvent` to capture `LoginPacket`, and pre-process the clientData JWT to ensure it doesn\u0027t 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.\n\nHowever, it\u0027s 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).\n\n### References\nAffected code:\n\nhttps://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L289-L303\nhttps://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L334-L350",
"id": "GHSA-xp4f-g2cm-rhg7",
"modified": "2026-04-15T19:43:33Z",
"published": "2026-04-15T19:43:33Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-xp4f-g2cm-rhg7"
},
{
"type": "WEB",
"url": "https://github.com/pmmp/PocketMine-MP/commit/c1d4a813fb8c21bfd8b9affd040da864b794df71"
},
{
"type": "PACKAGE",
"url": "https://github.com/pmmp/PocketMine-MP"
},
{
"type": "WEB",
"url": "https://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L289-L303"
},
{
"type": "WEB",
"url": "https://github.com/pmmp/PocketMine-MP/blob/5.41.1/src/network/mcpe/handler/LoginPacketHandler.php#L334-L350"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "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",
"type": "CVSS_V4"
}
],
"summary": "PocketMine-MP has LogDoS by many junk properties in client data JWT in LoginPacket"
}
Mitigation
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.
Mitigation
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.
Mitigation
Adjust configurations appropriately when the product is transitioned from a debug state to production.
No CAPEC attack patterns related to this CWE.