CVE-2026-62966

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/ESP32Async/ESPAsyncWebServer/commit/4efbd35e597d91f01749f2d4a14bb78fba8ea02e
https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-8m8p-vhxc-jmjw
https://github.com/ESP32Async/ESPAsyncWebServer/tree/v3.11.2

Configurations

No configuration.

History

30 Oct 2026, 21:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-30 21:17

Updated : 2026-10-30 21:17

NVD link : CVE-2026-62966

Mitre link : CVE-2026-62966

CVE.ORG link : CVE-2026-62966

JSON object : View

Products Affected

No product.

CWE

CWE-476

NULL Pointer Dereference

CWE-672

Operation on a Resource after Expiration or Release

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