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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-110306
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-20 07:17:08 UTC
Updated2026-10-20 20:17:14 UTC
Descriptionfast-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.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from ce714d77-add3-4f53-aff5-83d477b104bb

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS: 0.002040000 probability, percentile 0.098140000 (date 2026-10-20)

Problem Types: CWE-172 | CWE-180 | CWE-172 CWE-172: Encoding Error | CWE-180 CWE-180: Incorrect Behavior Order: Validate Before Canonicalize

VersionSourceTypeScoreSeverityVector
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNACVSS6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Fast-uri Fast-uri affected 2.4.8 semver Not specified
CNA Fast-uri Fast-uri unaffected 2.4.8 semver Not specified
CNA Fast-uri Fast-uri affected 3.0.0 3.1.9 semver Not specified
CNA Fast-uri Fast-uri unaffected 3.1.9 semver Not specified
CNA Fast-uri Fast-uri affected 4.0.0 4.2.3 semver Not specified
CNA Fast-uri Fast-uri unaffected 4.2.3 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org
github.com/fastify/fast-uri/security/advisories/GHSA-w74x-v6f9-j3xg ce714d77-add3-4f53-aff5-83d477b104bb github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: UlisesGascon (en)

CNA: mcollina (en)

CNA: zekth (en)

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