CVE-2026-42854 | arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ES… | CVSS 9.8 CRITICAL

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.

Metadata

CVE ID: CVE-2026-42854
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-04-30 16:44 UTC
Published: 2026-05-12 21:56 UTC
Last updated: 2026-05-13 14:24 UTC
Primary CWE: CWE-121
CWE-121: Stack-based Buffer Overflow
Vendor / Product: espressif / arduino-esp32
Sources: cve.org · NVD

Severity & Metrics

9.8 CRITICAL CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: PoC
Automatable: yes
Tech. Impact: total

Affected products (1)

Vendor	Product	Platform	Versions
espressif	arduino-esp32	—	< 3.3.8

Weakness (CWE)

CWE	Source	Description
CWE-121	cna	CWE-121: Stack-based Buffer Overflow

CVSS scores (1)

Score	Severity	Version	Source	Vector
9.8	CRITICAL	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References (1)

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