CVE-2026-73819: Ebyte Configuration Utility Auth Bypass

CVE-2026-73819 Overview

CVE-2026-73819 is an authentication bypass vulnerability affecting an Ebyte product's vendor configuration utility. The utility permits access to administrative functions without verifying the operator's identity under specific credential conditions. An unauthenticated attacker on an adjacent network can modify critical device settings or change access credentials. Successful exploitation can lock legitimate administrators out of the device. The flaw is tracked under CWE-1390: Weak Authentication and was published in the CISA ICS advisory ecosystem.

Critical Impact
An unauthenticated adjacent-network attacker can seize administrative control of the affected Ebyte device, alter configuration, and rotate credentials to deny access to legitimate operators.

Affected Products

Ebyte vendor configuration utility (specific product/model listed in the CISA ICS advisory)
Deployments where the utility is reachable on the adjacent network
Industrial control system (ICS) environments using the affected Ebyte device family

Discovery Timeline

2026-08-31 - CVE-2026-73819 published to the National Vulnerability Database
2026-09-01 - Last updated in NVD
2026-09-03 - EPSS score published at 0.528%

Technical Details for CVE-2026-73819

Vulnerability Analysis

The vulnerability resides in the vendor configuration utility shipped with the affected Ebyte product. The utility exposes administrative operations, including configuration writes and credential changes, over the network. Under certain credential conditions, the utility does not verify the identity of the operator issuing those requests. This design flaw allows an attacker who can reach the device to invoke privileged operations without presenting valid authentication material.

Because the attack does not require user interaction and executes without prior privileges, an adversary needs only network reachability to the management interface. Exploitation compromises confidentiality, integrity, and availability of the device: attackers can read configuration, alter operational parameters, and replace credentials. Locking out legitimate administrators disrupts operational technology processes and can prevent recovery without physical intervention.

Root Cause

The root cause is weak authentication in the administrative code path of the configuration utility [CWE-1390]. Authentication logic either accepts default, empty, or predictable credentials, or fails to enforce a required authentication step before executing sensitive operations. The utility trusts requests reaching the management channel rather than validating operator identity per-request.

Attack Vector

The attack vector is network-adjacent. An attacker positioned on the same broadcast domain or a reachable network segment sends crafted requests to the configuration utility's administrative endpoints. No authentication challenge is enforced under the affected credential conditions, so the requests execute with administrative privilege. Typical follow-on actions include changing the administrative password, rewriting network parameters, and disabling management access from the legitimate operator's workstation.

No public proof-of-concept or exploit code is currently available for CVE-2026-73819. Consult the CISA ICS Advisory ICSA-26-237-06 and the GitHub CSAF Document for authoritative technical details.

Detection Methods for CVE-2026-73819

Indicators of Compromise

Unexpected changes to device administrator credentials or configuration parameters that cannot be attributed to a scheduled change window.
Administrator lockouts or failed logins from previously working credentials on Ebyte configuration utilities.
Configuration write operations originating from workstations or hosts not on the approved management allow-list.

Detection Strategies

Baseline the Ebyte device configuration and alert on any drift, including credential rotation events and network parameter changes.
Inspect management network traffic for requests to the vendor configuration utility that lack an associated authentication exchange.
Correlate ICS asset inventory data with authentication logs to surface administrative sessions that bypass expected identity checks.

Monitoring Recommendations

Enable full packet capture or NetFlow on OT management VLANs where Ebyte devices reside and retain records for post-incident analysis.
Forward device syslog and configuration-change events to a centralized log platform for continuous review.
Alert on any new host initiating traffic to the configuration utility's administrative port from outside the sanctioned management subnet.

How to Mitigate CVE-2026-73819

Immediate Actions Required

Isolate affected Ebyte devices on a dedicated management VLAN reachable only from authorized engineering workstations.
Apply strict firewall or ACL rules that block adjacent-network access to the vendor configuration utility except from approved hosts.
Rotate all administrative credentials on affected devices and verify that no default or empty-credential conditions remain configured.
Audit recent configuration changes and administrator accounts for unauthorized modification.

Patch Information

Refer to the CISA ICS Advisory ICSA-26-237-06 and the associated CSAF document for vendor-supplied fixes and affected firmware versions. Apply the vendor-recommended firmware update as soon as it is validated in a test environment. If no patch is currently available, prioritize the compensating controls below.

Workarounds

Place affected devices behind a jump host or bastion that enforces multi-factor authentication before allowing access to the configuration utility.
Disable the vendor configuration utility on production units when it is not required for active administration.
Enforce physical port security and disable unused switch ports to reduce adjacent-network exposure.
Segment ICS networks according to ISA/IEC 62443 zone and conduit guidance to limit lateral reachability to management interfaces.