arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE

arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2 microcontrollers. Prior to 3.3.8, the WebServer multipart form parser in arduino-esp32 allocates a Variable Length Array (VLA) on the stack whose size is derived from an attacker-controlled HTTP header field (Content-Type: multipart/form-data; boundary=...) without enforcing any length limit. Sending a boundary string longer than ~8000 characters overflows the 8192-byte task stack of the loopTask, causing a crash and potential remote code execution. This vulnerability is fixed in 3.3.8.

Problem type

CWE-121: Stack-based Buffer Overflow

Affected products

espressif

arduino-esp32

< 3.3.8 - AFFECTED

References

https://github.com/espressif/arduino-esp32/security/advisories/GHSA-8cmm-3887-r32j

https://github.com/espressif/arduino-esp32/security/advisories/GHSA-8cmm-3887-r32j

x_refsource_CONFIRM

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-42854

Click to expand

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    "dateUpdated": "2026-05-12T21:56:33.437Z",
    "dateReserved": "2026-04-30T16:44:48.378Z",
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