CVE-2026-27649: WebSocket Auth Bypass Vulnerability

CVE-2026-27649 Overview

CVE-2026-27649 is a session hijacking vulnerability affecting WebSocket backend communications in electric vehicle (EV) charging station infrastructure. The WebSocket backend uses charging station identifiers to uniquely associate sessions but allows multiple endpoints to connect using the same session identifier. This implementation results in predictable session identifiers and enables session hijacking or shadowing, where the most recent connection displaces the legitimate charging station and receives backend commands intended for that station.

This vulnerability may allow unauthorized users to authenticate as other users or enable a malicious actor to cause a denial-of-service condition by overwhelming the backend with valid session requests.

Critical Impact

Attackers can hijack WebSocket sessions to impersonate legitimate charging stations, intercept backend commands, or cause denial-of-service conditions affecting EV charging infrastructure.

Affected Products

• CTEK EV Charging Station WebSocket Backend
• CTEK Charging Infrastructure Management Systems
• Related OCPP (Open Charge Point Protocol) Implementations

Discovery Timeline

• 2026-03-20 - CVE CVE-2026-27649 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-27649

Vulnerability Analysis

This vulnerability stems from insufficient session expiration mechanisms (CWE-613) in the WebSocket backend implementation used for managing EV charging station communications. The backend system relies on charging station identifiers to establish and maintain unique sessions between the central management system and individual charging points.

The core issue is that the session management mechanism does not properly invalidate or prevent duplicate session connections. When a new connection is established using an existing session identifier, the system accepts it rather than rejecting the duplicate, causing the newer connection to effectively "shadow" or displace the legitimate session. This design flaw allows attackers who can predict or obtain valid station identifiers to establish unauthorized sessions.

Root Cause

The root cause is improper session expiration and insufficient session uniqueness validation (CWE-613: Insufficient Session Expiration). The WebSocket backend fails to implement adequate controls to prevent multiple simultaneous connections using identical session identifiers. Charging station identifiers follow predictable patterns, making them susceptible to enumeration attacks. Combined with the lack of session binding mechanisms such as cryptographic tokens or IP validation, this creates a straightforward attack path for session hijacking.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can exploit this vulnerability through the following approach:

The attacker first identifies or enumerates valid charging station identifiers, which may follow predictable naming conventions or patterns. The attacker then initiates a WebSocket connection to the backend server using a target station's identifier. Due to the flawed session management, the backend accepts this new connection and routes subsequent commands to the attacker's endpoint instead of the legitimate charging station.

This enables two primary attack scenarios: session hijacking, where the attacker receives commands intended for the legitimate station, potentially gaining access to sensitive operational data; and denial-of-service, where legitimate stations are repeatedly disconnected as attackers flood the system with valid session requests.

Detection Methods for CVE-2026-27649

Indicators of Compromise

• Multiple WebSocket connections originating from different IP addresses using the same charging station identifier
• Unusual connection patterns showing rapid session establishment and termination cycles
• Backend logs showing station identifiers connecting from unexpected geographic locations
• Legitimate charging stations reporting frequent disconnection events

Detection Strategies

• Implement logging and alerting for duplicate session identifier usage across different source IPs
• Monitor WebSocket connection metadata for anomalous patterns such as connection frequency and geographic distribution
• Deploy network traffic analysis to identify enumeration attempts against the WebSocket endpoint
• Configure intrusion detection rules to flag multiple concurrent sessions per station identifier

Monitoring Recommendations

• Enable detailed WebSocket connection logging including source IP, timestamp, and session identifier
• Establish baseline connection patterns for legitimate charging stations to detect deviations
• Implement real-time alerting for session shadowing events where a new connection displaces an existing one
• Monitor for bulk connection attempts that may indicate denial-of-service attacks

How to Mitigate CVE-2026-27649

Immediate Actions Required

• Contact CTEK support for updated firmware or backend patches addressing this vulnerability
• Implement network segmentation to restrict WebSocket backend access to authorized IP ranges
• Deploy Web Application Firewall (WAF) rules to limit connection rates per identifier
• Enable enhanced logging to identify potential exploitation attempts

Patch Information

Organizations should consult the CISA ICS Advisory ICSA-26-078-06 for official guidance and remediation steps. Additional technical details are available in the GitHub CSAF File. Contact CTEK Support for vendor-specific patches and firmware updates.

Workarounds

• Implement IP allowlisting to restrict WebSocket connections to known charging station IP addresses
• Deploy mutual TLS (mTLS) authentication to cryptographically verify station identity
• Add rate limiting on the WebSocket endpoint to mitigate denial-of-service attempts
• Consider implementing session tokens with cryptographic binding rather than relying solely on station identifiers

Network administrators can implement connection restrictions using firewall rules or reverse proxy configurations to limit access to the WebSocket backend from trusted networks only. Additionally, monitoring solutions should be configured to alert on session anomalies until official patches are deployed.