CVE-2026-27778: WebSocket API DoS Vulnerability

CVE-2026-27778 Overview

CVE-2026-27778 is a high-severity vulnerability affecting a WebSocket Application Programming Interface (API) that lacks restrictions on the number of authentication requests. This absence of rate limiting creates conditions for attackers to conduct denial-of-service (DoS) attacks by suppressing or mis-routing legitimate charger telemetry, as well as enabling brute-force attacks to gain unauthorized access to the system.

This vulnerability falls under CWE-307 (Improper Restriction of Excessive Authentication Attempts), a well-documented weakness category where systems fail to implement adequate controls against repeated authentication attempts. In the context of electric vehicle (EV) charging infrastructure, this flaw poses significant operational and security risks.

Critical Impact

Attackers can exploit the missing rate limiting to overwhelm the WebSocket API with authentication requests, disrupting charger telemetry operations or systematically attempting credential combinations to gain unauthorized access to charging infrastructure.

Affected Products

• ePower Charging Infrastructure (WebSocket API Component)
• EV Charger Management Systems utilizing the affected WebSocket API
• Associated telemetry and monitoring systems

Discovery Timeline

• 2026-03-06 - CVE-2026-27778 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-27778

Vulnerability Analysis

The vulnerability exists within the WebSocket API responsible for handling authentication requests in electric vehicle charging infrastructure. The root issue stems from the complete absence of rate limiting mechanisms, which should normally restrict the number of authentication attempts from any single source within a defined time window.

WebSocket connections maintain persistent, bidirectional communication channels between clients and servers. When these channels lack proper authentication throttling, they become susceptible to abuse. An attacker can establish a WebSocket connection and rapidly submit authentication requests without encountering any blocking, delay, or lockout mechanisms.

The impact extends beyond simple credential theft. In EV charging environments, successful exploitation could allow attackers to manipulate charger telemetry data, potentially affecting billing systems, energy management, and operational monitoring. The network-based attack vector with low complexity makes this vulnerability accessible to remote attackers without requiring prior authentication or user interaction.

Root Cause

The vulnerability originates from improper restriction of excessive authentication attempts (CWE-307). The WebSocket API implementation fails to track and limit authentication request frequency, allowing unlimited attempts without implementing countermeasures such as:

• Connection rate limiting per IP address
• Authentication attempt thresholds with lockout periods
• Progressive delays between failed authentication attempts
• CAPTCHA or proof-of-work challenges after threshold violations

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability through two primary methods:

Denial-of-Service Attack: By flooding the WebSocket API with authentication requests, an attacker can exhaust server resources, prevent legitimate authentication attempts, and disrupt the flow of charger telemetry data. This could impact real-time monitoring and control of EV charging stations.

Brute-Force Attack: Without rate limiting, attackers can systematically attempt credential combinations at high speed. Depending on password complexity requirements, this approach could yield unauthorized access in a relatively short timeframe compared to systems with proper rate limiting controls.

The attack targets the WebSocket authentication endpoint, leveraging the persistent connection nature of WebSocket protocols to maintain rapid request submission without the overhead of establishing new connections for each attempt.

Detection Methods for CVE-2026-27778

Indicators of Compromise

• Abnormally high volume of WebSocket authentication requests from single IP addresses or IP ranges
• Sudden spikes in failed authentication attempts against the WebSocket API
• Unusual patterns in charger telemetry data transmission or reporting gaps
• Evidence of credential testing sequences in authentication logs
• Degraded performance or unavailability of charging management systems

Detection Strategies

• Implement network-level monitoring for excessive WebSocket connection establishment rates
• Deploy intrusion detection signatures targeting rapid authentication attempt patterns
• Configure SIEM rules to alert on authentication failure thresholds per source IP
• Monitor for anomalous traffic patterns to WebSocket endpoints during off-peak hours
• Analyze authentication logs for systematic credential enumeration attempts

Monitoring Recommendations

• Enable detailed logging of all WebSocket authentication events including source IP, timestamp, and result
• Establish baseline metrics for normal authentication request volumes and alert on deviations
• Implement real-time dashboards for monitoring charger telemetry consistency and availability
• Configure automated alerting for sustained authentication failure rates exceeding defined thresholds

How to Mitigate CVE-2026-27778

Immediate Actions Required

• Review and apply vendor patches addressing rate limiting for WebSocket authentication
• Implement network-level rate limiting at firewalls or load balancers for WebSocket endpoints
• Consider temporary IP-based access restrictions to limit exposure while implementing permanent fixes
• Enable enhanced logging to detect ongoing exploitation attempts
• Coordinate with ePower support for updated firmware or configuration guidance

Patch Information

Refer to the ePower Support Resource for the latest security updates and patch availability. Additional technical details are available through the CISA ICS Advisory (ICSA-26-062-07) and the associated CSAF documentation on GitHub.

Organizations should prioritize applying vendor-provided patches as soon as they become available, given the network-accessible nature of this vulnerability and its potential impact on critical charging infrastructure.

Workarounds

• Deploy web application firewalls (WAF) with custom rules to limit authentication request rates per connection
• Implement IP-based rate limiting at the network perimeter to restrict requests from individual sources
• Configure reverse proxies to enforce connection throttling for WebSocket endpoints
• Temporarily restrict WebSocket API access to trusted IP ranges or VPN connections if operationally feasible
• Consider implementing additional authentication factors to increase brute-force difficulty

# Example: Rate limiting configuration for nginx reverse proxy
# Add to location block handling WebSocket connections
limit_req_zone $binary_remote_addr zone=ws_auth:10m rate=5r/s;

location /ws/auth {
    limit_req zone=ws_auth burst=10 nodelay;
    proxy_pass http://backend_websocket;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}