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CVE-2025-69209

ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors

6.9 MediumFix available

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

References

Credits

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.18%Up 0.2 points since Jan 22, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.9

ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors

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

References

Credits

Record
CVE-2025-69209
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-120
Updated
2026-11-02
EUVDEUVD-2025-206313 6.9

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

References

Credits

Record
EUVD-2025-206313
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
NVD 6.9

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

References

Credits

Record
CVE-2025-69209
CVSS 4.0
6.9 MediumCVSS: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
Weakness
CWE-120
Updated
2026-11-02
OSV 6.9

ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors

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

References

Credits

Record
CVE-2025-69209
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-120
Updated
2026-11-02
OSVDEBIAN-CVE-2025-69209 6.9

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 - The Fixing Commit is available at the following link 1a6a417f89c8901dad646efce74ae9d3ddebfd59 ### References - ASEC-26-001 ArduinoCore-avr vXXXX Resolves Buffer Overflow Vulnerability ### Credits - Maxime Rossi Bellom and Ramtine Tofighi Shirazi from SecMate (https://secmate.dev/)

Record
DEBIAN-CVE-2025-69209
CVSS 4.0
6.9 MediumCVSS: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
Updated
2026-11-02
OSVUBUNTU-CVE-2025-69209 6.9

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 - The Fixing Commit is available at the following link 1a6a417f89c8901dad646efce74ae9d3ddebfd59 ### References - ASEC-26-001 ArduinoCore-avr vXXXX Resolves Buffer Overflow Vulnerability ### Credits - Maxime Rossi Bellom and Ramtine Tofighi Shirazi from SecMate (https://secmate.dev/)

Record
UBUNTU-CVE-2025-69209
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
arduino-core-avr
Debian:12
before 1.8.7+dfsg-1~deb12u1, plus listed versions
1.8.6+dfsg-11.8.6+dfsg-2
1.8.7+dfsg-1~deb12u1
arduino-core-avr
Debian:13
before 1.8.7+dfsg-1~deb13u1, plus listed versions
1.8.6+dfsg-21.8.7+dfsg-1~deb12u1
1.8.7+dfsg-1~deb13u1
arduino-core-avr
Debian:14
before 1.8.7+dfsg-1, plus listed versions
1.8.6+dfsg-21.8.7+dfsg-1~deb12u11.8.7+dfsg-1~deb13u1
1.8.7+dfsg-1
arduino-core-avr
Ubuntu:22.04:LTS
All versions, plus listed versions
1.8.3+dfsg1-11.8.4+dfsg1-1
None known
arduino-core-avr
Ubuntu:24.04:LTS
All versions, plus listed versions
1.8.6+dfsg-1
None known
arduino-core-avr
Ubuntu:25.10
All versions, plus listed versions
1.8.6+dfsg-1
None known
arduino-core-avr
Ubuntu:26.10
All versions, plus listed versions
1.8.6+dfsg-1
None known
arduino-core-avr
Ubuntu:26.04:LTS
All versions, plus listed versions
1.8.6+dfsg-1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-69209 is a medium vulnerability (CVSS 6.9) in Arduino Arduinocore-avr, published January 21, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. Fixed in arduino-core-avr 1.8.7+dfsg-1~deb12u1.

References

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