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Vulnerability record · CVE-2026-42854 · published 12 May 2026

CVE-2026-42854: Espressif arduino-esp32 stack-based buffer overflow vulnerability

EEspressif · Arduino Esp32

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.

9.8 CVSS 3.1 Critical EPSS 0.83% · top 44.2% CWE-121 · Stack-based buffer overflow
9.8CVSS 3.1 base score
0.83%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-42854), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.