CVE-2025-69209: 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...

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. ### 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/)

Metrics

CVSS 4.0

6.9/10

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.15%

4.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-120

References

Timeline

Published: Jan 21, 2026
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2025-69209?

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/)

How severe is CVE-2025-69209?

CVE-2025-69209 has a CVSS score of 6.9/10 (MEDIUM severity). The EPSS model estimates a 0.15% probability of exploitation in the next 30 days.

How do I fix CVE-2025-69209?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.