CVE-2026-31981: cmc XSS — Fix

Description

A Stored HTML Injection vulnerability was discovered in the Diagram tab and Graph view due to a shared input validation function being insufficiently restrictive. An authenticated user with administrative privileges can inject malicious HTML tags into N2OS configuration data through multiple input vectors. When a victim views the affected data in the Diagram tab and Graph view, the injected HTML renders in their browser, enabling phishing and possibly open redirect attacks. Full XSS exploitation and direct information disclosure are prevented by the existing input validation and Content Security Policy configuration.

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CVSS v3.1 Score

5.9

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L

EPSS — Exploit Prediction

0.0014

Probability of exploitation

0.04%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

Affected Products

Vendor	Product	Versions
nozominetworks	cmc	< 26.2.0
nozominetworks	guardian	< 26.2.0

References

Advisories & Patches

https://security.nozominetworks.com/NN-2026:8-01

Frequently Asked Questions

What is CVE-2026-31981? +

A Stored HTML Injection vulnerability was discovered in the Diagram tab and Graph view due to a shared input validation function being insufficiently restrictive. An authenticated user with administrative privileges can inject malicious HTML tags into N2OS configuration data through multiple input vectors. When a victim views the affected data in the Diagram tab and Graph view, the injected HTML renders in their browser, enabling phishing and possibly open redirect attacks. Full XSS exploitation and direct information disclosure are prevented by the existing input validation and Content Security Policy configuration. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-31981? +

CVE-2026-31981 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0014, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-31981? +

CVE-2026-31981 affects products from nozominetworks, specifically: cmc, guardian. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-31981? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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