PatchSiren cyber security CVE debrief
CVE-2026-38426 arendst CVE debrief
A buffer overflow vulnerability exists in arendst Tasmota firmware version 15.3.0.3 and earlier. The flaw resides in the Scripter driver (xdrv_10_scripter.ino), specifically within the fetch_jpg() function where a 40-byte boundary buffer (jpg_task.boundary[40]) is populated using strcpy() without adequate bounds checking. This allows a remote attacker to trigger memory corruption and potentially execute arbitrary code. The vulnerability was published to the CVE List on 27 May 2026 and carries a HIGH severity CVSS 3.1 score of 7.3. The NVD entry currently shows a status of 'Deferred'. No known exploitation in ransomware campaigns has been reported, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog.
- Vendor
- arendst
- Product
- Tasmota
- CVSS
- HIGH 7.3
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-05-27
- Original CVE updated
- 2026-05-27
- Advisory published
- 2026-05-27
- Advisory updated
- 2026-05-27
Who should care
Organizations and individuals deploying Tasmota-based IoT devices, particularly those utilizing the Scripter driver for automation scripts involving JPEG image fetching. Security teams managing IoT/OT networks, smart home integrators, and firmware maintainers should prioritize assessment and patching.
Technical summary
The vulnerability is a classic buffer overflow (CWE-120) in the Tasmota Scripter driver's JPEG fetching functionality. The fetch_jpg() function uses strcpy() to copy data into a fixed 40-byte boundary buffer (jpg_task.boundary[40]) without length validation. An attacker supplying an oversized boundary string in a JPEG fetch operation can overflow this buffer, corrupting adjacent memory. The network-accessible attack vector (AV:N), low attack complexity (AC:L), and lack of required privileges (PR:N) make this remotely exploitable. Successful exploitation could lead to arbitrary code execution on affected IoT devices running Tasmota firmware.
Defensive priority
HIGH
Recommended defensive actions
- Upgrade Tasmota firmware to a version newer than 15.3.0.3 when available
- Review and restrict network access to Tasmota device management interfaces
- Monitor vendor security advisories for official patch releases
- If using the Scripter driver with JPEG fetching capabilities, consider temporarily disabling or restricting the feature until patched
- Implement network segmentation to limit exposure of IoT devices to untrusted networks
Evidence notes
CVE description identifies affected component as xdrv_10_scripter.ino, fetch_jpg() function, with strcpy() usage on jpg_task.boundary[40] buffer. CVSS vector AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L confirms network attack vector with low complexity. Source references include GitHub repository for Tasmota source code at specific commit and a researcher-hosted advisory repository.
Official resources
2026-05-27T14:16:45.880Z