CVE-2025-69209
Severity CVSS v4.0:
MEDIUM
Type:
CWE-120
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Publication date:
21/01/2026
Last modified:
21/01/2026
Description
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.<br />
<br />
### Patches<br />
<br />
- 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)<br />
<br />
- The Fixing Commit is available at the following link [1a6a417f89c8901dad646efce74ae9d3ddebfd59](https://github.com/arduino/ArduinoCore-avr/pull/613/commits/1a6a417f89c8901dad646efce74ae9d3ddebfd59)<br />
<br />
### References<br />
<br />
- [ASEC-26-001 ArduinoCore-avr vXXXX Resolves Buffer Overflow Vulnerability](https://support.arduino.cc/hc/en-us/articles/XXXXX)<br />
<br />
### Credits<br />
<br />
- Maxime Rossi Bellom and Ramtine Tofighi Shirazi from SecMate (https://secmate.dev/)
Impact
Base Score 4.0
6.90
Severity 4.0
MEDIUM
References to Advisories, Solutions, and Tools
- https://github.com/arduino/ArduinoCore-avr/commit/82a8ad2fb33911d8927c7af22e0472b94325d1a7
- https://github.com/arduino/ArduinoCore-avr/pull/613
- https://github.com/arduino/ArduinoCore-avr/releases/tag/1.8.7
- https://github.com/arduino/ArduinoCore-avr/security/advisories/GHSA-pvx3-fm7w-6hjm
- https://support.arduino.cc/hc/en-us/articles/24985906702748-ASEC-26-001-ArduinoCore-AVR-v1-8-7-Resolves-Stack-Based-Buffer-Overflow-Vulnerability