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CVE-2026-110306

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

Medium6.1EPSS 0.25%
Published
Updated
Reserved
Assigned by
openjs

Description

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.

Timeline

  1. ID reserved

    By openjs

  2. · 7 days later

    Published

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-110306, by who scored it
Scored byCVSSScoreVector
openjsCNA (assigner)3.1Medium6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVDNVD · Awaiting Analysis3.1Medium6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS (exploitation in 30 days)
0.25% · top 84% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.1.

Weakness

Affected products

  • fast-uri · fast-uri

    • affected < 2.4.8
    • unaffected 2.4.8
    • affected 3.0.0 – < 3.1.9
    • unaffected 3.1.9
    • affected 4.0.0 – < 4.2.3
    • unaffected 4.2.3

Affected packages

From reviewed advisories of the GitHub Advisory Database.

References (2)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .