Vulnerability · Published May 12, 2026 · Assigned by GitHub_M

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

Critical 9.8

In plain English

A critical-severity stack buffer overflow in arduino-esp32 from espressif. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities).

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)0.6%top 52.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
espressif	arduino-esp32	< 3.3.8

Weakness: CWE-121 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

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