Stored HTML Injection in N2OS Diagram and Graph View

Executive Summary

CVE-2026-31981 is a Stored HTML Injection vulnerability found in the Diagram tab and Graph view of Nozomi Networks Guardian and CMC software versions before 26.2.0.

The vulnerability occurs because a shared input validation function is not restrictive enough, allowing an authenticated user with administrative privileges to inject malicious HTML tags into N2OS configuration data through multiple input vectors.

When other users view the affected data in the Diagram tab or Graph view, the injected HTML executes in their browsers, which can enable phishing or open redirect attacks.

However, full cross-site scripting (XSS) exploitation and direct information disclosure are prevented by existing input validation and Content Security Policy configurations.

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Impact Analysis

This vulnerability can impact you by allowing an authenticated administrative user to inject malicious HTML into configuration data that other users will view.

When the injected HTML renders in the browsers of other users, it can be used to conduct phishing attacks or open redirect attacks, potentially compromising user trust and security.

Although full XSS attacks and direct information disclosure are mitigated, the medium risk remains due to the possibility of social engineering and redirection to malicious sites.

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Mitigation Strategies

To mitigate the Stored HTML Injection vulnerability (CVE-2026-31981), you should upgrade the Guardian and CMC software to version 26.2.0 or later.

• Limit access to the web management interface using internal firewall features.
• Review administrative accounts and remove any unnecessary ones to reduce the risk of malicious input.

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Compliance Impact

The vulnerability allows an authenticated administrative user to inject malicious HTML into configuration data, which can be rendered in other users' browsers, potentially enabling phishing or open redirect attacks.

Although full cross-site scripting exploitation and direct information disclosure are mitigated by existing input validation and Content Security Policy, the presence of such a vulnerability could increase the risk of phishing attacks and unauthorized redirection, which may impact compliance with security requirements in standards like GDPR and HIPAA that mandate protection against unauthorized access and data integrity.

Organizations subject to these regulations should consider this vulnerability as a medium risk that could affect their security posture and compliance, and should apply recommended mitigations such as upgrading software, restricting administrative access, and reviewing accounts.

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