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Description

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.

PUBLISHED Reserved 2026-04-30 | Published 2026-05-12 | Updated 2026-05-13 | Assigner GitHub_M




CRITICAL: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem types

CWE-121: Stack-based Buffer Overflow

Product status

< 3.3.8
affected

References

github.com/...-esp32/security/advisories/GHSA-8cmm-3887-r32j exploit

github.com/...-esp32/security/advisories/GHSA-8cmm-3887-r32j

cve.org (CVE-2026-42854)

nvd.nist.gov (CVE-2026-42854)

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