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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products
esp32async:espasyncwebserver
References 4
https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6…
security-advisories@github.com
https://github.com/ESP32Async/ESPAsyncWebServer/pull/445
security-advisories@github.com
https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1
security-advisories@github.com
https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-f…
security-advisories@github.com