CVE-2026-110306 (GCVE-0-2026-110306)
Vulnerability from cvelistv5 – Published: 2026-10-20 07:03 – Updated: 2026-10-20 07:03
VLAI
EPSS
VEX
Title
fast-uri vulnerable to URI scheme spoofing via percent-encoded scheme decoding
Summary
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.
Severity
6.1 (Medium)
Assigner
References
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"packageURL": "pkg:npm/fast-uri",
"product": "fast-uri",
"vendor": "fast-uri",
"versions": [
{
"lessThan": "2.4.8",
"status": "affected",
"version": "0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "2.4.8",
"versionType": "semver"
},
{
"lessThan": "3.1.9",
"status": "affected",
"version": "3.0.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "3.1.9",
"versionType": "semver"
},
{
"lessThan": "4.2.3",
"status": "affected",
"version": "4.0.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "4.2.3",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "remediation reviewer",
"value": "UlisesGascon"
},
{
"lang": "en",
"type": "remediation reviewer",
"value": "mcollina"
},
{
"lang": "en",
"type": "reporter",
"value": "zekth"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "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."
}
],
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 6.1,
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-172",
"description": "CWE-172: Encoding Error",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-180",
"description": "CWE-180: Incorrect Behavior Order: Validate Before Canonicalize",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-20T07:03:47.312Z",
"orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
"shortName": "openjs"
},
"references": [
{
"url": "https://github.com/fastify/fast-uri/security/advisories/GHSA-w74x-v6f9-j3xg"
},
{
"url": "https://cna.openjsf.org/security-advisories.html"
}
],
"title": "fast-uri vulnerable to URI scheme spoofing via percent-encoded scheme decoding",
"x_generator": {
"engine": "cve-kit 1.0.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
"assignerShortName": "openjs",
"cveId": "CVE-2026-110306",
"datePublished": "2026-10-20T07:03:47.312Z",
"dateReserved": "2026-10-13T19:49:41.192Z",
"dateUpdated": "2026-10-20T07:03:47.312Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-110306",
"date": "2026-10-20",
"epss": "0.00204",
"percentile": "0.09814"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"packageURL": "pkg:npm/fast-uri",
"product": "fast-uri",
"vendor": "fast-uri",
"versions": [
{
"lessThan": "2.4.8",
"status": "affected",
"version": "0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "2.4.8",
"versionType": "semver"
},
{
"lessThan": "3.1.9",
"status": "affected",
"version": "3.0.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "3.1.9",
"versionType": "semver"
},
{
"lessThan": "4.2.3",
"status": "affected",
"version": "4.0.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "4.2.3",
"versionType": "semver"
}
]
}
],
"source": "ce714d77-add3-4f53-aff5-83d477b104bb"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"id": "CVE-2026-110306",
"lastModified": "2026-10-20T07:17:08.810",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.1,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 2.7,
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary"
}
]
},
"published": "2026-10-20T07:17:08.810",
"references": [
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"url": "https://cna.openjsf.org/security-advisories.html"
},
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"url": "https://github.com/fastify/fast-uri/security/advisories/GHSA-w74x-v6f9-j3xg"
}
],
"sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb",
"vulnStatus": "Received",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-172"
},
{
"lang": "en",
"value": "CWE-180"
}
],
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-10-20T11:09:01+00:00",
"cve": "CVE-2026-110306",
"id": "CVE-2026-110306",
"initial_release_date": "2026-10-20T07:03:47.312000+00:00",
"product_status:known_affected": "148",
"product_status:known_not_affected": "2",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "fast-uri: fast-uri: Cross-Site Scripting via improper URI scheme decoding",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110306.json",
"version": "3"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.