CVE-2026-77977: Ebyte Gateway Auth Bypass Vulnerability

CVE-2026-77977 Overview

CVE-2026-77977 affects Ebyte gateway products whose vendor configuration utility fails to enforce authentication before executing disruptive administrative actions when default credentials remain configured. An attacker with adjacent network access can reboot the device or restore factory settings without credentials. Successful exploitation results in loss of configuration and service availability on the targeted gateway. The weakness is tracked as Missing Authentication for Critical Function [CWE-306]. CISA published coordinated advisory ICSA-26-237-06 documenting the flaw.

Critical Impact
An unauthenticated adjacent attacker can reboot the gateway or reset it to factory defaults, causing configuration loss and denial of service across dependent industrial processes.

Affected Products

Ebyte gateway product (specific models identified in CISA advisory ICSA-26-237-06)
Deployments retaining vendor default credentials
Devices exposing the vendor configuration utility on adjacent network segments

Discovery Timeline

2026-08-28 - CVE-2026-77977 published to NVD
2026-08-31 - Last updated in NVD database

Technical Details for CVE-2026-77977

Vulnerability Analysis

The Ebyte gateway ships with a vendor configuration utility used to manage device state. Certain administrative endpoints in this utility execute privileged operations without validating the requesting session. When the device retains its factory-default credentials, the utility skips authentication entirely for actions such as reboot and factory reset. An attacker on the same layer-2 segment can invoke these actions directly. The result is complete loss of runtime configuration and interruption of gateway-mediated communications.

Root Cause

The root cause is Missing Authentication for Critical Function [CWE-306]. The configuration utility relies on the presence of non-default credentials as a gate for authentication enforcement. When defaults are unchanged, disruptive administrative operations become reachable without any credential check. This is a design flaw in the utility's authorization logic, not a memory-safety issue.

Attack Vector

Exploitation requires adjacent network access, meaning the attacker must reach the device on the same broadcast domain or logical adjacent segment. No user interaction and no prior privileges are required. The attacker sends administrative requests, such as reboot or factory-reset commands, to the vendor configuration utility. Because default credentials remain in place, the utility processes the request and executes the operation. Impact is limited to integrity and availability of the device itself; confidentiality is not directly affected.

No verified proof-of-concept code is publicly available. Refer to the CISA ICS Advisory ICSA-26-237-06 and the GitHub CSAF Document for coordinated technical details.

Detection Methods for CVE-2026-77977

Indicators of Compromise

Unexpected gateway reboots recorded in device event logs or upstream monitoring systems.
Sudden loss of custom configuration, reversion to factory defaults, or reappearance of default credentials on managed devices.
Administrative requests to the vendor configuration utility originating from unauthorized hosts on the adjacent network.

Detection Strategies

Monitor operational technology (OT) network segments for unauthorized traffic to Ebyte gateway management interfaces.
Correlate device availability drops with administrative protocol activity observed on the same segment.
Alert on any successful reboot or factory-reset command received from a source address not on an approved management allowlist.

Monitoring Recommendations

Enable syslog forwarding from gateways to a centralized log platform and alert on reboot or reset events.
Baseline expected management traffic and flag deviations, particularly commands issued outside change windows.
Track authentication state on each device and flag any gateway still using vendor default credentials.

How to Mitigate CVE-2026-77977

Immediate Actions Required

Replace vendor default credentials on all Ebyte gateway devices before any other remediation step.
Restrict access to the vendor configuration utility using VLAN segmentation and layer-2 access controls so only authorized management hosts can reach it.
Review CISA advisory ICSA-26-237-06 for the current list of affected models and vendor guidance.

Patch Information

At the time of publication, no vendor patch reference is included in the NVD entry. Consult the CISA ICS Advisory ICSA-26-237-06 and the corresponding GitHub CSAF Document for updated vendor remediation status and firmware availability.

Workarounds

Rotate all default administrative credentials on affected gateways, since authentication enforcement in the utility depends on non-default credentials being set.
Place gateways behind a dedicated management VLAN with strict access control lists limiting inbound traffic to known engineering workstations.
Disable the vendor configuration utility on production networks where it is not required for operations.
Monitor for unauthorized reboot or reset commands and physically inspect devices that show unexpected configuration loss.

bash

# Example: restrict management VLAN access to a single engineering workstation
# (adapt to your switch vendor syntax)
ip access-list extended EBYTE-MGMT
 permit tcp host 10.10.10.25 host 10.20.30.40 eq 80
 permit tcp host 10.10.10.25 host 10.20.30.40 eq 443
 deny   ip any host 10.20.30.40 log
 permit ip any any