ESP32Async ESPAsyncWebServer up to 3.11.1 Multipart Parser src/WebRequest.cpp null pointer dereference

Summaryinfo

A vulnerability was found in ESP32Async ESPAsyncWebServer up to 3.11.1. It has been declared as problematic. The impacted element is an unknown function of the file src/WebRequest.cpp of the component Multipart Parser. The manipulation results in null pointer dereference. This vulnerability is cataloged as CVE-2026-62966. The attack may be launched remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in ESP32Async ESPAsyncWebServer up to 3.11.1. It has been classified as problematic. Affected is some unknown processing of the file src/WebRequest.cpp of the component Multipart Parser. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-62966 since 07/15/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 3.11.2 eliminates this vulnerability.

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Productinfo

Type

• Web Server

Vendor

• ESP32Async

Name

• ESPAsyncWebServer

Version

• 3.11.0
• 3.11.1

Website

• Product: https://github.com/ESP32Async/ESPAsyncWebServer/

CPE 2.3info

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CPE 2.2info

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