CVE-2026-1693: PcVue Authentication Bypass Vulnerability

CVE-2026-1693 Overview

CVE-2026-1693 is a security vulnerability affecting ARC Informatique PcVue SCADA software where the deprecated OAuth Resource Owner Password Credentials (ROPC) grant type flow is still used by web services. This authentication weakness affects the WebVue, WebScheduler, TouchVue, and Snapvue features in PcVue versions 12.0.0 through 16.3.3, potentially allowing remote attackers to steal user credentials.

The ROPC flow requires users to provide their credentials directly to the client application, which then transmits them to the authorization server. This pattern is explicitly deprecated by OAuth 2.0 security best practices because it exposes credentials to the client application and increases the attack surface for credential theft.

Critical Impact

Remote attackers may exploit this deprecated authentication flow to intercept or steal user credentials from PcVue SCADA web interfaces, potentially compromising industrial control system access.

Affected Products

• PcVue SCADA version 12.0.0 through 16.3.3
• WebVue web interface component
• WebScheduler scheduling component
• TouchVue mobile interface component
• Snapvue visualization component

Discovery Timeline

• February 26, 2026 - CVE-2026-1693 published to NVD
• February 26, 2026 - Last updated in NVD database

Technical Details for CVE-2026-1693

Vulnerability Analysis

This vulnerability falls under CWE-477 (Use of Obsolete Function), where PcVue continues to implement the OAuth 2.0 Resource Owner Password Credentials (ROPC) grant type despite its deprecation in OAuth 2.0 Security Best Current Practice (RFC 6819 and draft-ietf-oauth-security-topics).

The ROPC flow was originally designed for legacy applications that could not support browser-based redirects. However, this flow fundamentally breaks the security model of OAuth by requiring the resource owner to share their credentials with the client application. In modern security contexts, this creates significant credential exposure risks, particularly in network-accessible industrial control system environments like SCADA.

The vulnerability affects multiple web-facing components of PcVue, expanding the potential attack surface across different entry points into the SCADA system.

Root Cause

The root cause is the continued implementation of the deprecated OAuth ROPC grant type in PcVue's web services authentication mechanism. Rather than migrating to more secure OAuth flows such as Authorization Code with PKCE (Proof Key for Code Exchange), the software maintains backward compatibility with the insecure ROPC pattern.

This design decision exposes user credentials to:

• The client application itself, which must handle plaintext credentials
• Network interception if TLS is not properly implemented or compromised
• Memory-based attacks on the client application
• Logging systems that may inadvertently capture credentials

Attack Vector

The attack vector is network-based and requires user interaction. An attacker positioned on the network path between users and the PcVue web services could potentially intercept credential transmissions. Additionally, compromised or malicious client applications could harvest credentials passed through the ROPC flow.

Since this vulnerability affects web-facing SCADA components, exploitation could provide attackers with legitimate user credentials to access industrial control interfaces, potentially leading to unauthorized monitoring or control of industrial processes.

The vulnerability mechanism involves the client application collecting username and password credentials directly from users and transmitting them to the PcVue authorization endpoint. Unlike modern OAuth flows where credentials are only handled by the authorization server, ROPC exposes credentials throughout the authentication chain. Technical details are available in the PCVue Security Bulletin SB2026-2.

Detection Methods for CVE-2026-1693

Indicators of Compromise

• Unusual authentication patterns in PcVue web service logs indicating credential harvesting attempts
• Network traffic analysis showing OAuth token requests using the password grant type
• Unauthorized access to WebVue, WebScheduler, TouchVue, or Snapvue interfaces with legitimate credentials
• Authentication attempts from unexpected geographic locations or IP addresses

Detection Strategies

• Monitor OAuth token endpoint requests for grant_type=password parameters in network traffic
• Implement authentication anomaly detection for PcVue web interfaces to identify credential abuse
• Deploy network intrusion detection rules to flag ROPC authentication flows
• Review PcVue access logs for successful authentications followed by suspicious activity patterns

Monitoring Recommendations

• Enable comprehensive logging on PcVue web services authentication endpoints
• Implement real-time alerting for authentication failures and anomalies on SCADA web interfaces
• Monitor for credential stuffing patterns against PcVue authentication endpoints
• Establish baseline authentication patterns to detect deviations indicating potential credential compromise

How to Mitigate CVE-2026-1693

Immediate Actions Required

• Review network segmentation to limit exposure of PcVue web services to trusted networks only
• Implement strong TLS configurations on all PcVue web service endpoints
• Enable multi-factor authentication if supported to reduce impact of credential theft
• Apply the latest PcVue security updates from ARC Informatique
• Monitor authentication logs for signs of credential abuse

Patch Information

ARC Informatique has released security information regarding this vulnerability. Organizations should consult the PCVue Security Bulletin SB2026-2 for official patch guidance and upgrade paths to versions that implement secure OAuth flows.

Administrators should plan to upgrade affected PcVue installations to versions that replace ROPC with modern OAuth 2.0 flows such as Authorization Code with PKCE.

Workarounds

• Restrict network access to PcVue web services using firewall rules and VPN requirements
• Implement network-level monitoring to detect and alert on ROPC authentication flows
• Deploy web application firewalls to add additional authentication controls
• Consider disabling affected web features (WebVue, WebScheduler, TouchVue, Snapvue) if not operationally required until patching is complete

# Example network restriction configuration
# Limit PcVue web service access to trusted internal networks
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP