How severe is CVE-2026-31873?

CVE-2026-31873 has a CVSS 3.x base score of 0.0, rated none severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability none.

Is CVE-2026-31873 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31873?

CVE-2026-31873 affects Unjs Unhead. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31873?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-31873 have an EU (EUVD) identifier?

Yes. CVE-2026-31873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11640.

When was CVE-2026-31873 published?

CVE-2026-31873 was published on 2026-03-12 and last updated on 2026-06-17.

CVE-2026-31873

CVE-2026-31873 is a none-severity vulnerability in Unjs Unhead with a CVSS 3.x base score of 0.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: None (CVSS 3.x base score 0.0)
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11640
Weakness: CWE-79
Affected product: Unjs Unhead
Published: 2026-03-12
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-31873?: 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.
How severe is CVE-2026-31873?: CVE-2026-31873 has a CVSS 3.x base score of 0.0, rated none severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability none.
Is CVE-2026-31873 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31873?: CVE-2026-31873 affects Unjs Unhead. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31873?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-31873 have an EU (EUVD) identifier?: Yes. CVE-2026-31873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11640.
When was CVE-2026-31873 published?: CVE-2026-31873 was published on 2026-03-12 and last updated on 2026-06-17.

References

https://github.com/unjs/unhead/security/advisories/GHSA-5339-hvwr-7582

Affected products (1)

cpe:2.3:a:unjs:unhead:*:*:*:*:*:*:*:*

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