CVE-2026-119756
CriticalCVSS 9.8Summary
Tasmota through 16.0.0 (fixed in commit e97e1e4) contains a heap out-of-bounds write in SendReceiveDeviceGroupMessage() that allows unauthenticated attackers on the local network to corrupt heap memory by sending crafted Device Groups messages over UDP port 4447. The messages cause the log_remaining counter to go negative and writes to exceed the fixed 512-byte buffer. This can crash the device or potentially achieve native code execution on ESP8266 and ESP32 platforms lacking ASLR and heap cookies.
Risk Assessment
An attacker on the local network can remotely crash IoT devices or potentially execute native code, leading to device takeover and further lateral movement. The risk applies to all Tasmota devices through version 16.0.0.
Recommendation
Upgrade Tasmota to a version containing commit e97e1e4 or later. Until patched, restrict access to UDP port 4447 to trusted network segments and segment IoT devices.
Other vulnerabilities in Tasmota
See all- CVE-2026-119755High
Tasmota through 16.0.0 (fixed in commit 1cb7ebc) contains a cross-site request forgery vulnerability that allows unauthenticated attackers to bypass Referer-based CSRF protection in HttpCheckPriviledgedAccess() by crafting a Referer header where the device hostname or IP appears as a substring immediately after http://evil.com/. Attackers can lure an administrator on the device's network to a malicious page to issue arbitrary console commands and reconfigure Wi-Fi, MQTT, settings, or firmware on devices lacking a WebPassword.
- CVE-2026-38427High
Tasmota versions up to 15.3.0.3 contain an issue in the fetch_jpg() function that allows a remote attacker to cause a heap buffer overflow. The Content-Length from a JPEG stream is stored in a uint16_t variable, leading to allocation of a smaller buffer than the data actually read when the value exceeds 65535.
Original NVD description (English source)
Tasmota through 16.0.0, fixed in commit e97e1e4, contains a heap out-of-bounds write vulnerability in SendReceiveDeviceGroupMessage() that allows unauthenticated attackers on the local network to corrupt heap memory by sending crafted Device Groups messages over UDP port 4447 that cause the log_remaining counter to go negative and writes to exceed the fixed 512-byte buffer. Attackers can exploit this flaw to crash the device or potentially achieve native code execution on ESP8266 and ESP32 platforms that lack ASLR and heap cookies.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS