Vulnerability-Lookup

CVE-2026-73492 (GCVE-0-2026-73492)

Vulnerability from cvelistv5 – Published: 2026-08-12 21:00 – Updated: 2026-08-12 21:00

Title

Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons

Summary

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.2, Loofah::HTML5::Scrub.allowed_uri? does not reject javascript: or vbscript: URIs whose scheme is split by semicolon-less numeric character references such as &#58, &#9, &#10, or &#13. CGI.unescapeHTML leaves these references encoded, so allowed_uri? reports the URL safe even though a browser decodes an encoded colon or strips encoded whitespace and executes the resulting URI scheme. This issue affects only callers that pass HTML-encoded strings directly to allowed_uri?; Loofah's default sanitize() path is not affected. This issue is fixed in version 2.25.2.

Severity

2.3 (Low)


                        
                          CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-184 - Incomplete List of Disallowed Inputs

Assigner

GitHub_M

References

4 references

URL	Tags
https://github.com/flavorjones/loofah/security/ad…	x_refsource_CONFIRM
https://github.com/flavorjones/loofah/pull/308	x_refsource_MISC
https://github.com/flavorjones/loofah/commit/f1be…	x_refsource_MISC
https://github.com/flavorjones/loofah/releases/ta…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
flavorjones	loofah	Affected: >= 2.25.0, < 2.25.2

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "loofah",
          "vendor": "flavorjones",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.25.0, \u003c 2.25.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.2, Loofah::HTML5::Scrub.allowed_uri? does not reject javascript: or vbscript: URIs whose scheme is split by semicolon-less numeric character references such as \u0026#58, \u0026#9, \u0026#10, or \u0026#13. CGI.unescapeHTML leaves these references encoded, so allowed_uri? reports the URL safe even though a browser decodes an encoded colon or strips encoded whitespace and executes the resulting URI scheme. This issue affects only callers that pass HTML-encoded strings directly to allowed_uri?; Loofah\u0027s default sanitize() path is not affected. This issue is fixed in version 2.25.2."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 2.3,
            "baseSeverity": "LOW",
            "privilegesRequired": "LOW",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-184",
              "description": "CWE-184: Incomplete List of Disallowed Inputs",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-12T21:00:24.679Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/flavorjones/loofah/security/advisories/GHSA-5qhf-9phg-95m2",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/flavorjones/loofah/security/advisories/GHSA-5qhf-9phg-95m2"
        },
        {
          "name": "https://github.com/flavorjones/loofah/pull/308",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/flavorjones/loofah/pull/308"
        },
        {
          "name": "https://github.com/flavorjones/loofah/commit/f1be9d893b5a8dd79240441a912d8897e74c38c0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/flavorjones/loofah/commit/f1be9d893b5a8dd79240441a912d8897e74c38c0"
        },
        {
          "name": "https://github.com/flavorjones/loofah/releases/tag/v2.25.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/flavorjones/loofah/releases/tag/v2.25.2"
        }
      ],
      "source": {
        "advisory": "GHSA-5qhf-9phg-95m2",
        "discovery": "UNKNOWN"
      },
      "title": "Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-73492",
    "datePublished": "2026-08-12T21:00:24.679Z",
    "dateReserved": "2026-08-12T19:00:33.735Z",
    "dateUpdated": "2026-08-12T21:00:24.679Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-73492\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-12T22:17:16.527\",\"lastModified\":\"2026-08-12T22:17:16.527\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.2, Loofah::HTML5::Scrub.allowed_uri? does not reject javascript: or vbscript: URIs whose scheme is split by semicolon-less numeric character references such as \u0026#58, \u0026#9, \u0026#10, or \u0026#13. CGI.unescapeHTML leaves these references encoded, so allowed_uri? reports the URL safe even though a browser decodes an encoded colon or strips encoded whitespace and executes the resulting URI scheme. This issue affects only callers that pass HTML-encoded strings directly to allowed_uri?; Loofah\u0027s default sanitize() path is not affected. This issue is fixed in version 2.25.2.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"flavorjones\",\"product\":\"loofah\",\"versions\":[{\"version\":\"\u003e= 2.25.0, \u003c 2.25.2\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":2.3,\"baseSeverity\":\"LOW\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"LOW\",\"subIntegrityImpact\":\"LOW\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-79\"},{\"lang\":\"en\",\"value\":\"CWE-184\"}]}],\"references\":[{\"url\":\"https://github.com/flavorjones/loofah/commit/f1be9d893b5a8dd79240441a912d8897e74c38c0\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/flavorjones/loofah/pull/308\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/flavorjones/loofah/releases/tag/v2.25.2\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/flavorjones/loofah/security/advisories/GHSA-5qhf-9phg-95m2\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}

GHSA-5QHF-9PHG-95M2

Vulnerability from github – Published: 2026-07-21 22:03 – Updated: 2026-07-21 22:03

Summary

Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons

Details

Summary

Loofah::HTML5::Scrub.allowed_uri? does not correctly reject javascript: or vbscript: URIs when the scheme is split by a numeric character reference that has no trailing semicolon. A browser decodes such references and resolves the URL to an executable javascript: scheme, while allowed_uri? reports it safe.

This is a bypass of the fix for GHSA-46fp-8f5p-pf2m, which handled numeric character references with a trailing ; (	, 
, ) but did not cover the forms without semicolons.

Details

allowed_uri? decodes HTML entities with CGI.unescapeHTML, which decodes numeric character references only when they carry a trailing ;. A reference without a semicolon such as : (colon) or 	 (tab) is left literal, so the scheme-detection check finds no scheme, and the method falls through to its scheme-less path and returns true.

A browser, however, decodes numeric character references even without a trailing semicolon. An encoded colon such as : becomes the : scheme separator, so javascript&#58alert(1) resolves to javascript:alert(1). Encoded whitespace such as &#9 (tab) is decoded and then stripped from the URL, rejoining the surrounding text, so java&#9script:alert(1) also resolves to javascript:alert(1). In both cases the URL executes while allowed_uri? approved it as safe.

Note that Loofah's default sanitize() path is not affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public allowed_uri? string-level helper that pass it HTML-encoded strings.

Impact

Callers that validate a user-controlled URL with Loofah::HTML5::Scrub.allowed_uri? and then render the approved value into an href or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call allowed_uri? directly, as well as higher-level features built on top of it, such as Action Text 8.2's markdown link validation.

Mitigation

Upgrade to Loofah >= 2.25.2.

Credit

Responsibly reported by GitHub user @MoonFuji.

;

Severity

2.3 (Low)


                  
                    CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "loofah"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.25.0"
            },
            {
              "fixed": "2.25.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-184",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T22:03:11Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "## Summary\n\n`Loofah::HTML5::Scrub.allowed_uri?` does not correctly reject `javascript:` or `vbscript:` URIs when the scheme is split by a numeric character reference that has no trailing semicolon. A browser decodes such references and resolves the URL to an executable `javascript:` scheme, while `allowed_uri?` reports it safe.\n\nThis is a bypass of the fix for [GHSA-46fp-8f5p-pf2m](https://github.com/flavorjones/loofah/security/advisories/GHSA-46fp-8f5p-pf2m), which handled numeric character references with a trailing `;` (`\u0026#9;`, `\u0026#10;`, `\u0026#13;`) but did not cover the forms without semicolons.\n\n## Details\n\n`allowed_uri?` decodes HTML entities with `CGI.unescapeHTML`, which decodes numeric character references only when they carry a trailing `;`. A reference without a semicolon such as `\u0026#58` (colon) or `\u0026#9` (tab) is left literal, so the scheme-detection check finds no scheme, and the method falls through to its scheme-less path and returns `true`.\n\nA browser, however, decodes numeric character references even without a trailing semicolon. An encoded colon such as `\u0026#58` becomes the `:` scheme separator, so `javascript\u0026#58alert(1)` resolves to `javascript:alert(1)`. Encoded whitespace such as `\u0026#9` (tab) is decoded and then stripped from the URL, rejoining the surrounding text, so `java\u0026#9script:alert(1)` also resolves to `javascript:alert(1)`. In both cases the URL executes while `allowed_uri?` approved it as safe.\n\nNote that Loofah\u0027s default `sanitize()` path is **not** affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public `allowed_uri?` string-level helper that pass it HTML-encoded strings.\n\n## Impact\n\nCallers that validate a user-controlled URL with `Loofah::HTML5::Scrub.allowed_uri?` and then render the approved value into an `href` or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call `allowed_uri?` directly, as well as higher-level features built on top of it, such as Action Text 8.2\u0027s markdown link validation.\n\n## Mitigation\n\nUpgrade to Loofah \u003e= 2.25.2.\n\n## Credit\n\nResponsibly reported by GitHub user @MoonFuji.",
  "id": "GHSA-5qhf-9phg-95m2",
  "modified": "2026-07-21T22:03:11Z",
  "published": "2026-07-21T22:03:11Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/security/advisories/GHSA-5qhf-9phg-95m2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/commit/f1be9d893b5a8dd79240441a912d8897e74c38c0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/flavorjones/loofah"
    },
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/releases/tag/v2.25.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons"
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

CVE-2026-73492 (GCVE-0-2026-73492)

GHSA-5QHF-9PHG-95M2

Summary

Details

Impact

Mitigation

Credit

Tags

Sightings

Nomenclature