ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1.
History

Mon, 21 Sep 2026 22:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
First Time appeared Esp32async
Esp32async espasyncwebserver
Vendors & Products Esp32async
Esp32async espasyncwebserver

Thu, 17 Sep 2026 18:45:00 +0000

Type Values Removed Values Added
Description ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1.
Title ESPAsyncWebServer: Integer overflow in multipart boundary parser causes denial of service
Weaknesses CWE-190
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-09-17T18:28:26.977Z

Updated: 2026-09-21T21:05:49.373Z

Reserved: 2026-06-15T19:15:27.343Z

Link: CVE-2026-54571

cve-icon Vulnrichment

Updated: 2026-09-21T21:05:41.594Z

cve-icon NVD

Status : Deferred

Published: 2026-09-17T19:16:50.843

Modified: 2026-09-24T21:25:27.050

Link: CVE-2026-54571

cve-icon Redhat

No data.