Vulnerability 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.
Related Weaknesses (CWE)
References
- https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a
- https://github.com/ESP32Async/ESPAsyncWebServer/pull/445
- https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1
- https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fc
FAQ
What is CVE-2026-54571?
CVE-2026-54571 is a documented vulnerability. 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 _boundaryPosi...
How severe is CVE-2026-54571?
CVSS scoring is not yet available for CVE-2026-54571. Check NVD for updates.
Is there a patch for CVE-2026-54571?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.