CVE-2021-43936

CRITICAL EXPLOITED

webhmi_firmware < 4.1 - Unrestricted Upload of File with Dangerous Type

Title source: llm
STIX 2.1

Exploitation Summary

CVE-2021-43936 has been observed exploited in the wild (reported by VulnCheck KEV). EIP tracks 2 public exploits from researchers including Jeremiasz Pluta, LongWayHomie.

AI-analyzed exploit summary This exploit leverages an authenticated file upload vulnerability in WebHMI Firmware < 4.1 to achieve remote code execution. It uploads a malicious PHP file and triggers a reverse shell via a crafted GET request.

Description

The software allows the attacker to upload or transfer files of dangerous types to the WebHMI portal, that may be automatically processed within the product's environment or lead to arbitrary code execution.

Exploits (2)

exploitdb WORKING POC
by Jeremiasz Pluta · pythonwebappsphp
https://www.exploit-db.com/exploits/50589

This exploit leverages an authenticated file upload vulnerability in WebHMI Firmware < 4.1 to achieve remote code execution. It uploads a malicious PHP file and triggers a reverse shell via a crafted GET request.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: WebHMI Firmware < 4.1
Auth required
Prerequisites: Valid credentials for WebHMI · Network access to target · Netcat listener on attacker machine
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC 8 stars
by LongWayHomie · remote
https://github.com/LongWayHomie/CVE-2021-43936

This is a functional exploit for CVE-2021-43936, targeting WebHMI Firmware < 4.1. It authenticates, uploads a malicious PHP file, and triggers a reverse shell via command injection.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: WebHMI Firmware < 4.1
Auth required
Prerequisites: Network access to target · Valid admin credentials · Netcat listener on attacker machine
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (2)

Core 2
Core References
Patch, Third Party Advisory, US Government Resource x_refsource_misc
https://us-cert.cisa.gov/ics/advisories/icsa-21-336-03
Exploit, Third Party Advisory, VDB Entry x_refsource_misc
http://packetstormsecurity.com/files/165252/WebHMI-4.0-Remote-Code-Execution.html

Scores

CVSS v3 10.0
EPSS 0.3580
EPSS Percentile 98.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Details

VulnCheck KEV 2024-05-09
CWE
CWE-434
Status published
Products (1)
webhmi/webhmi_firmware < 4.1
Published Dec 06, 2021
Tracked Since Feb 18, 2026