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VulnerabilityPublished Updated

CVE-2026-39315: unjs unhead · Incomplete List of Disallowed Inputs

Affects unjs unheadSource CVE Database V5

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Not known to be exploited · CVSS 6.1 Medium : upgrade to 2.1.13 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.1.13
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade unhead and unjs/unhead to 2.1.13.

Affected software

ProductAffectedFixed in
unjsunheadAffected
  • <2.1.13
Fixed in
  • 2.1.13
GitHubunjs/unheadpkg:github/unjs/unheadOther threatsAffected
  • <2.1.13
Fixed in
  • 2.1.13

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability is fixed in unhead version 2.1.13. Users should upgrade to version 2.1.13 or later to remediate this issue. Patch status is not explicitly confirmed in the vendor advisory content provided, but the description states the issue is fixed in 2.1.13. No other mitigation steps are indicated.

Description

Unhead is a document head and template manager. Prior to 2.1.13, useHeadSafe() is the composable that Nuxt's own documentation explicitly recommends for rendering user-supplied content in <head> safely. Internally, the hasDangerousProtocol() function in packages/unhead/src/plugins/safe.ts decodes HTML entities before checking for blocked URI schemes (javascript:, data:, vbscript:). The decoder uses two regular expressions with fixed-width digit caps. The HTML5 specification imposes no limit on leading zeros in numeric character references. When a padded entity exceeds the regex digit cap, the decoder silently skips it. The undecoded string is then passed to startsWith('javascript:'), which does not match.makeTagSafe() writes the raw value directly into SSR HTML output. The browser's HTML parser decodes the padded entity natively and constructs the blocked URI. This vulnerability is fixed in 2.1.13.

References

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