CVE-2025-69209

Date: January 21, 2026

ArduinoCore-avr contains the source code and configuration files of the Arduino AVR Boards platform. A vulnerability in versions prior to 1.8.7 allows an attacker to trigger a stack-based buffer overflow when converting floating-point values to strings with high precision. By passing very large "decimalPlaces" values to the affected String constructors or concat methods, the "dtostrf" function writes beyond fixed-size stack buffers, causing memory corruption and denial of service. Under specific conditions, this could enable arbitrary code execution on AVR-based Arduino boards. Patches - The Fix is included starting from the "1.8.7" release available from the following link "ArduinoCore-avr v1.8.7" (https://github.com/arduino/ArduinoCore-avr) - The Fixing Commit is available at the following link "1a6a417f89c8901dad646efce74ae9d3ddebfd59" (https://github.com/arduino/ArduinoCore-avr/pull/613/commits/1a6a417f89c8901dad646efce74ae9d3ddebfd59) References - "ASEC-26-001 ArduinoCore-avr vXXXX Resolves Buffer Overflow Vulnerability" (https://support.arduino.cc/hc/en-us/articles/XXXXX) Credits - Maxime Rossi Bellom and Ramtine Tofighi Shirazi from SecMate (https://secmate.dev/)