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Vulnerabilities

Security fix · CVE-2026-110306

fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js.

Published Oct 20, 2026 · catalog updated Oct 23, 2026 · fast-uri is a dependency-free

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-110306. EPSS is 0.25%. Act only if a listed version of fast-uri is a dependency-free is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (fast-uri is a dependency-free).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.25%
Remediation
Version ranges on file
Affected products
npm fast-uri

fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, fast-uri percent-decodes the scheme component with the legacy global unescape() function before validating it, so an input whose decoded scheme is a dangerous token is emitted as a live scheme even though RFC 3986 does not allow percent-encoding in a scheme and no other parser accepts it. An application that screens dangerous schemes on the raw input and then stores or renders the normalized or resolved result can turn an inert string into an executable javascript, data, or vbscript URL, producing a stored or reflected cross-site scripting vector, and the equal() comparison treats an encoded and a plain scheme as the same, which can bypass equality-based allowlists. The issue is fixed in fast-uri 2.4.8, 3.1.9, and 4.2.3, and users should upgrade to one of these versions or later. As a workaround, reject input whose scheme part contains a percent sign, or check the parsed scheme against an allowlist after normalization and use that same parsed result rather than the raw string.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • npm fast-uri< 2.4.8
  • npm fast-uri>= 3.0.0, < 3.1.9
  • npm fast-uri>= 4.0.0, < 4.2.3

How to fix CVE-2026-110306

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-110306. EPSS is 0.25%. Act only if a listed version of fast-uri is a dependency-free is installed.

Which versions are affected?

Compare what you have installed with < 2.4.8, >= 3.0.0, < 3.1.9, >= 4.0.0, < 4.2.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-172; CWE-180. EPSS 0.25%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 20, 2026 · NIST NVD

    Detected

    fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, fast-uri percent-decodes the scheme component with the legacy global unescape() function before validating it, so an input whose decoded scheme is a dangerous token is emitted as a live scheme even though RFC 3986 does not allow percent-enc

  2. Oct 20, 2026 · NIST NVD

    Updated

    fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, fast-uri percent-decodes the scheme component with the legacy global unescape() function before validating it, so an input whose decoded scheme is a dangerous token is emitted as a live scheme even though RFC 3986 does not allow percent-enc

  3. Oct 23, 2026 · GitHub Advisory Database

    Updated

    ### Impact percent-decodes the scheme component with the legacy global before validating it, so an input whose decoded scheme is a valid but dangerous token is emitted as a live scheme. RFC 3986 section 3.1 does not allow percent-encoding in a scheme, so no RFC or WHATWG parser treats such input as having that scheme, but does. For example, returns , returns , and returns . The form ( ) produces t

Sources

  • CVE.orgVulnerability recordCVE-2026-110306

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-110306

    30-day exploitation probability 0.25%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-w74x-v6f9-j3xg

    fast-uri vulnerable to URI scheme spoofing via percent-encoded scheme decoding

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-110306

    fast-uri percent-decodes the scheme component with the legacy global unescape() before validating it, so an input whose decoded scheme is a valid but dangerous token is emitted as a live scheme. RFC 3986 section 3.1 does not allow percent-encoding in a scheme, so no RFC or WHATWG parser treats such input as having that scheme, but fast-uri does. For example, normalize('%6Aavascript:alert(1)') retu

    advisories.gitlab.com
  • NIST NVDVulnerability recordCVE-2026-110306

    fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, fast-uri percent-decodes the scheme component with the legacy global unescape() function before validating it, so an inp

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • GitLab Advisory DatabaseOct 27, 2026
  • GitHub Advisory DatabaseOct 24, 2026
  • CVE.orgOct 21, 2026
  • NIST NVDOct 21, 2026