CVE-2026-1698 is a vulnerability classified under CWE-644, indicating improper neutralization of HTTP headers for scripting syntax. This flaw exists in arcinfo's PcVue software, specifically versions 15.0.0 through 16.3.3, affecting the WebClient and WebScheduler web applications. The vulnerability targets three authentication-related endpoints: /Authentication/ExternalLogin, /Authentication/AuthorizationCodeCallback, and /Authentication/Logout. Due to insufficient sanitization of the HTTP Host header, an attacker can craft malicious Host header values that inject harmful payloads. These payloads can manipulate server-side logic, potentially altering authentication flows or session management. The attack vector is network-based (AV:N), requires no privileges (PR:N), and no authentication (AT:N), but does require user interaction (UI:P), such as tricking a user into visiting a malicious link. The impact primarily affects confidentiality with limited integrity and availability consequences. The vulnerability has a CVSS 4.0 score of 5.3, indicating medium severity. No public exploits or patches are currently available, but the vulnerability is published and should be addressed promptly. This issue is particularly relevant for organizations relying on PcVue for industrial control and automation, where compromised authentication mechanisms can lead to unauthorized access or control manipulation.

The vulnerability allows remote attackers to inject malicious payloads via the HTTP Host header, potentially manipulating server-side authentication and session handling in PcVue WebClient and WebScheduler applications. This can lead to unauthorized access or information disclosure, undermining confidentiality. While the impact on integrity and availability is limited, exploitation could facilitate further attacks or unauthorized actions within industrial control environments. Given PcVue's role in critical infrastructure and industrial automation, successful exploitation could disrupt operational processes or expose sensitive operational data. The requirement for user interaction reduces the likelihood of automated widespread exploitation, but targeted attacks against organizations using vulnerable PcVue versions remain a significant risk. The absence of known exploits in the wild currently limits immediate threat but does not diminish the urgency for remediation.

Organizations should immediately assess their PcVue deployments to identify affected versions (15.0.0 through 16.3.3). Since no official patches are currently available, implement the following mitigations: 1) Employ web application firewalls (WAFs) to detect and block suspicious or malformed Host header values targeting the specified endpoints. 2) Restrict access to the WebClient and WebScheduler applications to trusted networks or VPNs to reduce exposure. 3) Monitor logs for anomalous requests containing unusual Host headers or suspicious authentication activity. 4) Educate users about phishing risks to minimize successful user interaction exploitation. 5) Coordinate with arcinfo for timely patch releases and apply updates promptly once available. 6) Consider implementing additional input validation or header sanitization at reverse proxies or load balancers to neutralize malicious headers before reaching the application. 7) Conduct penetration testing focused on HTTP header injection to verify the effectiveness of mitigations.