CVE-2026-54571
ESPAsyncWebServer: Integer overflow in multipart boundary parser causes denial of service
CVSS Score
0.0
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-190 |
| Vendor | esp32async |
| Product | espasyncwebserver |
| Published | Sep 17, 2026 |
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Affected Versions
ESP32Async / ESPAsyncWebServer
< 3.11.1
References
github.com: https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4 github.com: https://github.com/ESP32Async/ESPAsyncWebServer/pull/445 github.com: https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f github.com: https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1