Is CVE-2026-31873 actively exploited?

No active exploitation of CVE-2026-31873 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-31873 be exploited remotely?

Yes. CVE-2026-31873 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-31873?

CVE-2026-31873 has a CVSS score of 6.1 (MEDIUM).

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MEDIUM

CVE-2026-31873

CWE-79Published: March 12, 2026· Updated: Mar 16, 2026

6.1

CVSS v3.1

EPSS:0.03%probability of exploitation in 30 daysPercentile:8.4th

Official Description

Unhead is a document head and template manager. Prior to 2.1.11, The link.href check in makeTagSafe (safe.ts) uses String.includes(), which is case-sensitive. Browsers treat URI schemes case-insensitively. DATA:text/css,... is the same as data:text/css,... to the browser, but 'DATA:...'.includes('data:') returns false. An attacker can inject arbitrary CSS for UI redressing or data exfiltration via CSS attribute selectors with background-image callbacks. This vulnerability is fixed in 2.1.11.

NVD Source

Technical Analysis

CVE-2026-31873 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.