CVE-2026-77847 Overview
CVE-2026-77847 is a hard-coded credential vulnerability [CWE-798] affecting Tycon Systems TPDIN-Monitor-WEB3 versions 2.2.9 and prior. The flaw allows an attacker with adjacent network access to intercept sensitive information or credentials by leveraging embedded credentials shipped in the device firmware. Tycon Systems TPDIN-Monitor-WEB3 is an industrial control system (ICS) component used for monitoring Power over Ethernet (PoE) infrastructure, and CISA published an ICS advisory (ICSA-26-246-08) covering the issue. Because credentials are embedded in firmware, standard password rotation cannot remediate the exposure without a firmware update.
Critical Impact
An adjacent-network attacker can use hard-coded credentials to intercept sensitive information or credentials handled by the TPDIN-Monitor-WEB3 device.
Affected Products
- Tycon Systems TPDIN-Monitor-WEB3 version 2.2.9
- Tycon Systems TPDIN-Monitor-WEB3 versions prior to 2.2.9
- Fixed in TPDIN-Monitor-WEB3 firmware version 2.4.2
Discovery Timeline
- 2026-09-04 - CVE-2026-77847 published to the National Vulnerability Database (NVD)
- 2026-09-09 - Last updated in NVD database
Technical Details for CVE-2026-77847
Vulnerability Analysis
The vulnerability stems from the use of hard-coded credentials embedded within the TPDIN-Monitor-WEB3 firmware. Hard-coded credentials [CWE-798] are authentication values compiled into a product that cannot be changed by an administrator without a firmware update. An attacker who obtains or extracts these credentials can authenticate to the device or decrypt intercepted traffic without exploiting any other flaw. According to the CVE description, successful exploitation allows an attacker to intercept sensitive information or credentials handled by the device.
Because the attack vector is adjacent network, the attacker must be on the same logical or physical network segment as the device. This constraint is typical for ICS and PoE monitoring equipment deployed on isolated operational technology (OT) segments.
Root Cause
The root cause is the presence of static credentials embedded in the firmware image of TPDIN-Monitor-WEB3 versions 2.2.9 and prior. These credentials are identical across every affected deployment, so extraction from a single unit exposes the entire installed base. Tycon Systems addressed the issue by releasing firmware version 2.4.2, which removes the vulnerable credential handling.
Attack Vector
Exploitation requires adjacent network access to the TPDIN-Monitor-WEB3 device. An attacker positioned on the same network segment can use the hard-coded credentials to authenticate to management interfaces or to intercept and decrypt sensitive traffic that relies on the embedded credential material. No user interaction or prior privileges are required.
No public proof-of-concept exploit is currently listed for CVE-2026-77847, and CISA has not added it to the Known Exploited Vulnerabilities catalog. See the CISA ICS Advisory ICSA-26-246-08 for the vendor-coordinated technical write-up.
Detection Methods for CVE-2026-77847
Indicators of Compromise
- Successful authentication events to TPDIN-Monitor-WEB3 management interfaces from hosts that are not designated OT engineering workstations.
- Unexpected configuration changes, firmware reads, or credential exports originating from the device.
- Anomalous packet captures or port mirroring sessions on the OT segment hosting the device.
Detection Strategies
- Inventory all TPDIN-Monitor-WEB3 devices and confirm firmware version; any device reporting a version at or below 2.2.9 is affected.
- Baseline authentication and administrative activity to the device, and alert on sessions from unapproved sources.
- Monitor OT network segments for reconnaissance behavior such as ARP scanning, HTTP/HTTPS probes, or SNMP walks targeting the device's IP.
Monitoring Recommendations
- Forward device logs and network telemetry from OT segments to a centralized analytics platform for correlation with enterprise identity and endpoint data.
- Track outbound connections from the device that deviate from documented management flows.
- Review access control lists (ACLs) and VLAN segmentation logs regularly to confirm the device is not reachable from unauthorized networks.
How to Mitigate CVE-2026-77847
Immediate Actions Required
- Upgrade TPDIN-Monitor-WEB3 firmware to version 2.4.2 using the vendor-provided Tycon Systems Firmware Update or the Tycon Systems Hex File.
- Restrict management access to the device to a dedicated OT management VLAN with strict ACLs.
- Audit any accounts or systems that may have relied on the embedded credentials and rotate any dependent secrets after the upgrade.
Patch Information
Tycon Systems has released firmware version 2.4.2 for TPDIN-Monitor-WEB3 that remediates CVE-2026-77847. Administrators should validate the update against the vendor artifacts and follow the guidance in the CISA ICS Advisory ICSA-26-246-08 and the GitHub CSAF JSON Document.
Workarounds
- Place affected devices behind a firewall and block adjacent network access from any host that does not require management connectivity.
- Disable or restrict remote management protocols on the device until the firmware update can be applied.
- Enforce network segmentation between IT and OT environments to reduce the adjacent-network attack surface.
# Example ACL restricting TPDIN-Monitor-WEB3 management access to a jump host
# Replace TPDIN_IP and JUMP_HOST_IP with values for your environment
access-list 110 permit ip host JUMP_HOST_IP host TPDIN_IP
access-list 110 deny ip any host TPDIN_IP log
access-list 110 permit ip any any
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
