Arduino ArduinoCore-avr up to 1.8.7 String dtostrf buffer overflow

Summaryinfo

A vulnerability was found in Arduino ArduinoCore-avr up to 1.8.7 and classified as critical. This impacts the function dtostrf of the component String. Such manipulation leads to buffer overflow. This vulnerability is documented as CVE-2026-48490. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Arduino ArduinoCore-avr up to 1.8.7. It has been rated as critical. Affected by this issue is the function dtostrf of the component String. The manipulation with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. CVE summarizes:

ArduinoCore-avr contains the source code and configuration files of the Arduino AVR Boards platform. A vulnerability in versions prior to 1.8.8 allows an attacker to trigger a stack-based buffer overflow when concatenating floating-point values of sufficiently large magnitude onto an Arduino String object. By passing values near the extremes of the float or double range to `String::concat(float)`, `String::concat(double)`, `String::operator+=()`, or the `+` operator with a float/double operand, `dtostrf()` writes beyond the fixed-size stack buffer, causing memory corruption and denial of service. Under specific conditions, this could enable arbitrary code execution on AVR-based Arduino boards. The fix is included starting from the `1.8.8 `release.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-48490 since 05/21/2026. The exploitation is known to be easy. The attack may be launched remotely. Technical details are known, but there is no available exploit.

Upgrading to version 1.8.8 eliminates this vulnerability.

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Productinfo

Vendor

• Arduino

Name

• ArduinoCore-avr

Version

• 1.8.0
• 1.8.1
• 1.8.2
• 1.8.3
• 1.8.4
• 1.8.5
• 1.8.6
• 1.8.7

Website

• Product: https://github.com/arduino/ArduinoCore-avr/

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