CVE-2026-76945: Ebyte Device Auth Bypass Vulnerability

CVE-2026-76945 Overview

CVE-2026-76945 affects Ebyte industrial devices that rely on client-managed authentication tokens without adequate server-side validation. An attacker on the network can replay or manipulate authentication tokens to reach administrative functionality. The flaw is classified under CWE-603: Use of Client-Side Authentication. CISA published the issue in advisory ICSA-26-237-06, placing it in the industrial control systems (ICS) domain. The vulnerability requires no privileges and no user interaction, and it exposes confidential device data to remote attackers.

Critical Impact
Remote, unauthenticated attackers can replay or forge authentication tokens to access administrative functions on affected Ebyte devices.

Affected Products

Ebyte industrial device (specific model listed in CISA advisory ICSA-26-237-06)
Not Available
Not Available

Discovery Timeline

2026-08-28 - CVE-2026-76945 published to the National Vulnerability Database (NVD)
2026-08-31 - Last updated in NVD database

Technical Details for CVE-2026-76945

Vulnerability Analysis

The vulnerability stems from the device's decision to trust authentication tokens supplied and managed by the client. The server accepts these tokens without verifying integrity, freshness, or binding to a validated session. An attacker who observes or crafts a token can reuse it to invoke administrative endpoints. Because the flow is network-reachable and requires no credentials or user interaction, exploitation is straightforward for an attacker with access to the device's management interface. Successful exploitation compromises confidentiality by exposing administrative data and configuration. The advisory maps the weakness to CWE-603, which covers reliance on client-side authentication.

Root Cause

The device delegates authentication state to the client. Tokens are not cryptographically bound to a server-issued session, are not validated for replay, and lack sufficient server-side checks. This design choice removes the server as the authoritative trust boundary for administrative access.

Attack Vector

An unauthenticated attacker with network access to the management interface captures or manipulates a valid authentication token. The attacker replays the modified token against administrative endpoints. The server accepts the token and grants access to administrative functionality. Technical details for reproduction are described in the CISA ICS Advisory ICSA-26-237-06 and its accompanying CSAF document.

No verified proof-of-concept code has been published. Refer to the CISA advisory for authoritative technical details.

Detection Methods for CVE-2026-76945

Indicators of Compromise

Repeated administrative requests carrying identical or slightly altered authentication tokens from unexpected source addresses.
Successful administrative actions preceded by no interactive login sequence in device logs.
Configuration changes on Ebyte devices originating from IP addresses outside authorized management ranges.

Detection Strategies

Inspect management-plane traffic for token reuse across sessions, source IPs, or user agents.
Alert on administrative endpoint access that lacks a corresponding preceding authentication event on the same device.
Baseline normal management access windows and flag off-hours administrative activity against ICS assets.

Monitoring Recommendations

Forward device syslog and management HTTP logs to a centralized platform for correlation and long-term retention.
Monitor for outbound connections from Ebyte devices to unfamiliar destinations that could indicate post-compromise activity.
Track configuration state changes on affected devices and compare against approved change tickets.

How to Mitigate CVE-2026-76945

Immediate Actions Required

Restrict network access to affected Ebyte device management interfaces using firewalls or ACLs, limiting reachability to a small set of trusted administrative hosts.
Place affected devices on isolated OT network segments and block Internet exposure of management ports.
Review recent administrative activity logs on affected devices for signs of token replay or unauthorized configuration change.

Patch Information

At the time of publication, no vendor patch is referenced in the NVD entry. Consult the CISA ICS Advisory ICSA-26-237-06 and Ebyte's official channels for vendor remediation guidance and firmware updates. Apply firmware updates as soon as the vendor releases them.

Workarounds

Enforce VPN or jump-host access for all management sessions to affected Ebyte devices.
Rotate any long-lived credentials or tokens issued to device operators and disable shared accounts.
Apply CISA's recommended ICS defensive measures, including network segmentation and minimizing device exposure per ICSA-26-237-06.

bash

# Example: restrict management access to a trusted administrative subnet
# (adapt interface names and addresses to your environment)
iptables -A INPUT -p tcp --dport 80 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP