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CVE-2026-42854— arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE

Quick assessment

Affected
espressif arduino-esp32
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

arduino-esp32是Espressif开源的一个用于 ESP32、ESP32-S2、ESP32-S3、ESP32-C3、ESP32-C6 和 ESP32-H2 的 Arduino 内核。 arduino-esp32 3.3.8之前版本存在安全漏洞，该漏洞源于WebServer多部分表单解析器在栈上分配可变长度数组，其大小由攻击者控制的HTTP标头字段决定而不限制长度，可能导致栈溢出和潜在远程代码执行。

CVSS 9.8 · Critical EPSS 0.83% · P56

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
espressif arduino-esp32 < 3.3.8 affected
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I. Basic Information for CVE-2026-42854

Vulnerability Information
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Vulnerability Title
arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
栈缓冲区溢出
Source: CVE Program / CVE List V5
Vulnerability Title
arduino-esp32 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
arduino-esp32是Espressif开源的一个用于 ESP32、ESP32-S2、ESP32-S3、ESP32-C3、ESP32-C6 和 ESP32-H2 的 Arduino 内核。 arduino-esp32 3.3.8之前版本存在安全漏洞，该漏洞源于WebServer多部分表单解析器在栈上分配可变长度数组，其大小由攻击者控制的HTTP标头字段决定而不限制长度，可能导致栈溢出和潜在远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
espressif arduino-esp32 < 3.3.8 -

II. Public POCs for CVE-2026-42854

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III. Intelligence Information for CVE-2026-42854

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Vendor Advisories for CVE-2026-42854 (1)

IV. Related Vulnerabilities

Same product: arduino-esp32
Same vendor: espressif
Same weakness: CWE-121

V. Comments for CVE-2026-42854

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