CVE-2026-62966
Dashboard / Vulnerabilities / CVE-2026-62966
Summary: ESPAsyncWebServer multipart parser has null-pointer write
Details: 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.
References: https://github.com/ESP32Async/ESPAsyncWebServer/tree/v3.11.2, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62966.json, https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-8m8p-vhxc-jmjw, https://nvd.nist.gov/vuln/detail/CVE-2026-62966, https://github.com/ESP32Async/ESPAsyncWebServer/commit/4efbd35e597d91f01749f2d4a14bb78fba8ea02e
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