CVE-2026-1698 is a vulnerability classified under CWE-644, which involves improper neutralization of HTTP headers for scripting syntax. This flaw affects arcinfo's PcVue product, specifically the WebClient and WebScheduler web applications in versions 15.0.0 through 16.3.3. The vulnerability resides in three authentication-related endpoints: /Authentication/ExternalLogin, /Authentication/AuthorizationCodeCallback, and /Authentication/Logout. An attacker can exploit this by sending crafted HTTP Host headers that are not properly sanitized by the server, allowing injection of malicious payloads. These payloads can manipulate server-side behavior, potentially leading to attacks such as web cache poisoning, cross-site scripting (XSS), or other header injection-based exploits. The vulnerability is remotely exploitable without requiring authentication but does require user interaction, such as clicking a malicious link. The CVSS 4.0 base score is 5.3, indicating a medium severity level, with network attack vector, low complexity, no privileges required, and user interaction needed. The impact primarily affects confidentiality and integrity, with limited availability impact. No patches or exploits are currently publicly available, but the vulnerability is published and should be addressed promptly. The flaw highlights the importance of proper input validation and neutralization of HTTP headers to prevent injection attacks in web applications, especially those handling authentication flows.

The vulnerability allows remote attackers to inject malicious payloads via HTTP Host headers into critical authentication endpoints of PcVue WebClient and WebScheduler applications. This can lead to manipulation of server-side logic, potentially enabling web cache poisoning, session fixation, or cross-site scripting attacks. Such attacks may compromise user credentials, session integrity, or lead to unauthorized actions within the affected web applications. Organizations relying on PcVue for industrial automation or critical infrastructure management could face confidentiality breaches or integrity violations, impacting operational security. Although availability impact is limited, the manipulation of authentication flows could disrupt user access or trust in the system. The medium severity rating reflects the moderate risk posed by this vulnerability, but exploitation could be leveraged as part of a broader attack chain. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers often target industrial control systems. The vulnerability's presence in widely used versions means many organizations globally could be exposed if unpatched.

1. Apply vendor patches or updates as soon as they become available for PcVue WebClient and WebScheduler applications to remediate the vulnerability. 2. In the absence of patches, implement web application firewall (WAF) rules to detect and block suspicious or malformed HTTP Host headers targeting the affected endpoints. 3. Enforce strict validation and sanitization of HTTP headers on the server side, particularly for Host headers, to neutralize scripting syntax and prevent injection. 4. Monitor authentication endpoints for unusual request patterns or header anomalies that could indicate exploitation attempts. 5. Educate users about phishing and social engineering risks since exploitation requires user interaction. 6. Conduct regular security assessments and penetration testing focusing on header injection and authentication flows. 7. Restrict access to the affected endpoints via network segmentation or VPNs where feasible to reduce exposure. 8. Implement HTTP Strict Transport Security (HSTS) and Content Security Policy (CSP) headers to mitigate the impact of injection attacks. 9. Review and harden web server and proxy configurations to reject invalid Host headers. 10. Maintain up-to-date incident response plans to quickly address any exploitation attempts.