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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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-38426 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-38426

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-38426 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-38426

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.