ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to version 3.11.2, the multipart parser in "src/WebRequest.cpp" frees "_itemBuffer" and sets it to NULL when "BOUNDARY_OR_DATA" matches the closing boundary of a file part, before confirming the following terminator, while leaving "_itemIsFile" true. If the next byte is neither the final closing dashes nor a clean CRLF, the "DASH3_OR_RETURN2" or "EXPECT_FEED2" rewind branch re-injects provisionally consumed bytes through "itemWriteByte". Because "_itemIsFile" remains true, "_itemBuffer"["_itemBufferIndex"++] writes through a null pointer. On ESP32 this causes a "StoreProhibited" exception, panic and device reboot, producing remote denial of service. A route with a non-trivial body/upload handler, such as a file-upload or web-OTA endpoint, must be present. This issue is fixed in version 3.11.2.