CVE-2026-20748: WebSocket Backend Auth Bypass Vulnerability

CVE-2026-20748 Overview

CVE-2026-20748 is a session hijacking vulnerability in WebSocket backend implementations that utilize charging station identifiers for session management. The vulnerability arises from the use of predictable session identifiers and the allowance of multiple endpoints to connect using the same session identifier. This design flaw enables session hijacking or shadowing attacks, where a malicious actor's connection can displace a legitimate charging station and intercept backend commands intended for that station.

Critical Impact

This vulnerability enables unauthorized authentication as other users and can facilitate denial-of-service attacks by overwhelming the backend with valid session requests, potentially disrupting electric vehicle charging infrastructure operations.

Affected Products

• WebSocket backend implementations using charging station identifiers for session management
• Electric vehicle charging station management systems
• Industrial Control Systems (ICS) with WebSocket-based communication

Discovery Timeline

• 2026-03-06 - CVE CVE-2026-20748 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-20748

Vulnerability Analysis

This vulnerability is classified under CWE-613 (Insufficient Session Expiration), though its core issue extends to predictable session identifier generation and improper session management. The WebSocket backend architecture uses charging station identifiers as unique session keys, which creates a fundamental security flaw when these identifiers are predictable or enumerable.

When a malicious actor connects to the WebSocket backend using a known or guessed charging station identifier, the backend accepts this connection and associates it with that station's session. The most recent connection takes precedence, effectively shadowing or displacing the legitimate charging station's connection. This allows the attacker to receive all backend commands and messages originally intended for the authentic charging station.

The network-accessible nature of this vulnerability means attackers do not require local access or special privileges to exploit it. The attack can be executed remotely against exposed WebSocket endpoints.

Root Cause

The root cause stems from improper session management implementation that relies solely on charging station identifiers without additional authentication factors or session validation mechanisms. The system fails to verify the legitimacy of connecting endpoints and does not implement proper session binding or cryptographic session tokens. Additionally, the absence of mutual authentication allows any endpoint to claim a session identity without proof of authorization.

Attack Vector

The attack leverages the network-exposed WebSocket backend and proceeds through identifier enumeration or prediction. An attacker can observe or guess charging station identifiers, then establish a WebSocket connection using a legitimate station's identifier. Once connected, the attacker's session displaces the authentic station's connection, allowing interception of backend commands. This session shadowing technique can be used for:

• Unauthorized authentication: Impersonating legitimate charging stations to access sensitive commands or data
• Denial of Service: Flooding the backend with connection requests using valid identifiers to exhaust resources or disrupt legitimate station operations
• Command interception: Receiving and potentially manipulating commands intended for legitimate charging infrastructure

The vulnerability can be exploited without user interaction and requires no authentication, making it particularly concerning for publicly accessible charging infrastructure.

Detection Methods for CVE-2026-20748

Indicators of Compromise

• Multiple WebSocket connections from different IP addresses using the same charging station identifier
• Rapid connection/disconnection patterns suggesting session takeover attempts
• Unusual geographic distribution of connection sources for individual charging station identifiers
• Backend log entries showing session displacement events or duplicate identifier warnings

Detection Strategies

• Implement monitoring for WebSocket connection patterns that indicate identifier reuse from multiple sources
• Deploy anomaly detection to identify connection attempts using sequential or predictable station identifiers
• Configure alerting for session displacement events where existing connections are terminated by new connections
• Establish baseline behavioral profiles for legitimate charging stations and alert on deviations

Monitoring Recommendations

• Enable detailed logging of WebSocket connection metadata including source IP, connection timestamps, and session identifiers
• Monitor for enumeration patterns such as sequential connection attempts across charging station identifier ranges
• Implement real-time alerting for session shadowing events where legitimate stations report unexpected disconnections
• Track and correlate connection patterns across the charging infrastructure network

How to Mitigate CVE-2026-20748

Immediate Actions Required

• Review and audit WebSocket backend configurations for exposed endpoints
• Implement additional authentication mechanisms beyond charging station identifiers
• Enable rate limiting on WebSocket connection attempts per identifier
• Deploy network segmentation to limit exposure of WebSocket endpoints to trusted networks only

Patch Information

Consult the CISA ICS Advisory for vendor-specific remediation guidance and patch availability. Additionally, review the GitHub CSAF JSON Document for detailed vulnerability metadata and affected product information.

Organizations should contact their charging infrastructure vendors for specific firmware or software updates that address this session management vulnerability.

Workarounds

• Implement cryptographic session tokens that cannot be predicted or enumerated in addition to station identifiers
• Deploy mutual TLS (mTLS) authentication to verify both client and server identities before establishing WebSocket sessions
• Configure network-level access controls to restrict WebSocket endpoint access to known charging station IP ranges
• Enable session binding that ties WebSocket connections to additional factors such as client certificates or hardware attestation
• Implement session monitoring to detect and automatically terminate suspicious duplicate identifier connections

# Example network-level access control configuration
# Restrict WebSocket endpoint access to trusted charging station networks
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP