CVE-2026-42854 arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE
Remote attackers can trigger a stack buffer overflow in the WebServer multipart parser, potentially causing crashes or executing arbitrary code on ESP32 devices.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42854?
CVE-2026-42854 is a critical memory corruption vulnerability in espressif arduino-esp32, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-121
Which versions are affected by CVE-2026-42854?
It affects 1 product.
Products include Espressif Arduino-Esp32.
How do I fix CVE-2026-42854?
No fix has been published for CVE-2026-42854 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-42854 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42854 exists.
Other vulnerabilities in espressif arduino-esp32
Sources
Also known as GHSA-8cmm-3887-r32j.