# CVE-2026-119756: Tasmota 16.0.0 Heap Out-of-Bounds Write via Device Groups UDP

Status: published. Published: 2026-11-09. Updated: 2026-11-09.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/arendst/Tasmota/commit/e97e1e4f7e319a55caa1613aef1f25fc81bdb554

## Affected products and versions

- arendst / Tasmota (arendst/Tasmota): ≥ 0; ≤ 16.0.0 (affected, semver); e97e1e4f7e319a55caa1613aef1f25fc81bdb554 (unaffected, git). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 9.3 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 9.3 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable yes; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-805

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/arendst/Tasmota/commit/e97e1e4f7e319a55caa1613aef1f25fc81bdb554 (CNA: VulnCheck; patch, issue-tracking)

- https://www.vulncheck.com/advisories/tasmota-heap-out-of-bounds-write-via-device-groups-udp (CNA: VulnCheck; third-party-advisory)

- https://github.com/arendst/Tasmota/commit/e97e1e4f7e319a55caa1613aef1f25fc81bdb554 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/tasmota-heap-out-of-bounds-write-via-device-groups-udp (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-119756; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-119756; retrieved 2026-11-10; source updated 2026-11-09

Revision: 7bf3b9172b19e0ad2147c62822f4b1b6b3c31f17443221528ba60907ca07a283

Canonical: https://y2.dev/cve/CVE-2026-119756

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