CVE-2026-76940 Overview
CVE-2026-76940 is an authentication weakness affecting Ebyte industrial devices. The device fails to restrict repeated authentication attempts through rate limiting or account lockout mechanisms. Attackers can perform automated credential guessing attacks against deployments that rely on password-based authentication. The issue is categorized under [CWE-307: Improper Restriction of Excessive Authentication Attempts]. CISA published the flaw as part of ICS Advisory ICSA-26-237-06, indicating operational technology exposure.
Critical Impact
Unauthenticated network-based attackers can launch unlimited brute-force or credential stuffing attacks against Ebyte device login interfaces, leading to full account compromise.
Affected Products
- Ebyte industrial device (specific model identifiers listed in ICSA-26-237-06)
- Deployments relying on password-based authentication on the affected device
- Operational technology environments running the affected firmware
Discovery Timeline
- 2026-08-28 - CVE-2026-76940 published to NVD
- 2026-08-31 - Last updated in NVD database
Technical Details for CVE-2026-76940
Vulnerability Analysis
The affected Ebyte device exposes a password-based authentication interface without any control on the frequency or volume of login attempts. There is no rate limiting, no throttling, no CAPTCHA, and no account lockout after failed attempts. An attacker on the network can iterate through password dictionaries at machine speed until valid credentials are discovered.
Authentication weaknesses of this class are particularly serious in operational technology environments where devices often ship with default or weak passwords and are rarely rotated. Successful compromise grants the attacker whatever privileges the authenticated account holds on the device, which typically includes configuration and control functions.
Root Cause
The root cause is the absence of anti-automation controls on the authentication path. The device does not track failed authentication attempts per source, per account, or globally. It does not enforce increasing delays, temporary lockouts, or permanent lockouts. This maps directly to [CWE-307].
Attack Vector
The vulnerability is exploitable over the network with no privileges and no user interaction. An attacker only needs reachability to the device's authentication endpoint and a wordlist of candidate credentials. Automated tools such as Hydra or custom scripts can iterate through credential pairs unimpeded. No verified public exploit code has been published, and CISA KEV does not list this CVE at the time of writing. Refer to the CISA ICS Advisory ICSA-26-237-06 for vendor-specific technical detail.
Detect Identity Attacks the Moment Authentication Fails
Singularity™ Identity surfaces credential misuse, lateral movement, and privilege escalation in real time, so you can contain the breach before it spreads.
Stop Identity AttacksDetection Methods for CVE-2026-76940
Indicators of Compromise
- High volume of authentication attempts against Ebyte device management interfaces from a single or distributed set of source addresses.
- Successful logins immediately preceded by repeated failed authentication events on the same account.
- Configuration changes on the device following an unusual authentication pattern.
Detection Strategies
- Ingest device authentication logs into a centralized SIEM and alert on failed-login thresholds per source and per account.
- Deploy network intrusion detection signatures for known brute-force tool user-agents and connection patterns targeting the device's management protocol.
- Correlate authentication anomalies with subsequent administrative actions to identify successful brute-force outcomes.
Monitoring Recommendations
- Continuously monitor east-west and north-south traffic to OT device management ports for repeated short-lived TCP sessions.
- Baseline normal administrative login volume for each device and alert on deviations.
- Track outbound connections from the device that could indicate post-compromise activity.
How to Mitigate CVE-2026-76940
Immediate Actions Required
- Restrict network access to the device's authentication interface using firewall rules, VLAN segmentation, or a jump host so only authorized administrators can reach it.
- Replace any default or weak passwords with long, unique credentials, and rotate credentials used on affected devices.
- Place affected devices behind a VPN or bastion that itself enforces rate limiting and multi-factor authentication.
Patch Information
Refer to the CISA ICS Advisory ICSA-26-237-06 and the corresponding CSAF advisory file for the current vendor remediation status. Apply firmware updates from Ebyte as they become available and validate that the updated firmware enforces lockout or rate-limiting behavior.
Workarounds
- Terminate authentication in front of the device using an authenticating reverse proxy or ICS-aware gateway that enforces lockout after a small number of failed attempts.
- Restrict management access to a dedicated administration network reachable only through MFA-protected jump hosts.
- Disable password-based access on any device management protocol where certificate-based or key-based alternatives are supported.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
