{"id":"CVE-2026-54571","title":"ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350","summary":"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 _parseMu…","severity":"high","cvss":8.7,"cvssVector":"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","cwe":["CWE-190"],"vendor":"ESP32Async","product":"ESPAsyncWebServer","affected":["ESPAsyncWebServer < 3.11.1"],"published":"2026-09-17","updated":"2026-09-17","sourceUpdated":"2026-09-17T19:16:50.843","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-54571","references":[{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f","label":"security-advisories@github.com"},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/pull/445","label":"security-advisories@github.com"},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1","label":"security-advisories@github.com"},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4","label":"security-advisories@github.com"}],"tags":["nvd","cve.org"],"cvssSource":"cna","ingestedAt":"2026-09-17T19:26:25.318Z","epss":0.00301,"epssPercentile":0.22979,"slug":"CVE-2026-54571","body":"## Overview\n\nESPAsyncWebServer 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":47.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}