GHSA-VG3J-HPM9-8V5V

Vulnerability from github – Published: 2026-03-10 18:22 – Updated: 2026-09-02 13:35
VLAI
Summary
Craft CMS has a potential information disclosure vulnerability in preview tokens
Details

Summary

Craft CMS has a CSRF issue in the preview token endpoint at /actions/preview/create-token. The endpoint accepts an attacker-supplied previewToken.

Because the action does not require POST and does not enforce a CSRF token, an attacker can force a logged-in victim editor to mint a preview token chosen by the attacker.

That token can then be used by the attacker (without authentication) to access previewed/unpublished content tied to the victim’s authorized preview scope.

Preconditions

  • Victim is logged in to Craft control panel.
  • Victim has active preview authorization in session for target content (e.g., opened/edited an entry).
  • The attacker must know the target’s canonicalId and public URL path of that entry.

1) Attacker prepares a fixed token

Use any 32-character value, for example:

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

2) CSRF victim into minting that token

Send the victim a link (or top-level redirect) such as:

https://TARGET/actions/preview/create-token?elementType=craft%5Celements%5CEntry&canonicalId=123&siteId=1&previewToken=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&redirect=https%3A%2F%2FTARGET%2F

If the victim is logged in and authorized for previewElement:123, Craft creates that exact token.

3) Attacker accesses preview content unauthenticated

curl -i 'https://TARGET/news/known-entry-slug?token=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'

Expected vulnerable behavior:

  • Response renders preview/unpublished state (draft/provisional context), not just normal public content.

Impact

  • CSRF-based minting of attacker-known preview tokens.
  • Unauthorized access to draft/provisional/revision content via token replay.
  • Stealthy one-click exploitation against logged-in editors/admins.
  • No dependency on forwarded-host poisoning.
Severity
2.3 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0-RC1"
            },
            {
              "fixed": "4.17.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0-RC1"
            },
            {
              "fixed": "5.9.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-29113"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287",
      "CWE-352"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-10T18:22:02Z",
    "nvd_published_at": "2026-03-10T20:16:38Z",
    "severity": "LOW"
  },
  "details": "# Summary\n\nCraft CMS has a CSRF issue in the preview token endpoint at `/actions/preview/create-token`.  The endpoint accepts an attacker-supplied `previewToken`.\n\nBecause the action does not require POST and does not enforce a CSRF token, an attacker can force a logged-in victim editor to mint a preview token chosen by the attacker.  \n\nThat token can then be used by the attacker (without authentication) to access previewed/unpublished content tied to the victim\u2019s authorized preview scope.\n\n---\n\n## Preconditions\n- Victim is logged in to Craft control panel.\n- Victim has active preview authorization in session for target content (e.g., opened/edited an entry).\n- The attacker must know the target\u2019s `canonicalId` and public URL path of that entry.\n\n## 1) Attacker prepares a fixed token\nUse any 32-character value, for example:\n```text\naaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n```\n\n## 2) CSRF victim into minting that token\nSend the victim a link (or top-level redirect) such as:\n```text\nhttps://TARGET/actions/preview/create-token?elementType=craft%5Celements%5CEntry\u0026canonicalId=123\u0026siteId=1\u0026previewToken=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\u0026redirect=https%3A%2F%2FTARGET%2F\n```\n\nIf the victim is logged in and authorized for `previewElement:123`, Craft creates that exact token.\n\n## 3) Attacker accesses preview content unauthenticated\n```bash\ncurl -i \u0027https://TARGET/news/known-entry-slug?token=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\u0027\n```\n\nExpected vulnerable behavior:\n\n- Response renders preview/unpublished state (draft/provisional context), not just normal public content.\n\n---\n\n# Impact\n- CSRF-based minting of attacker-known preview tokens.\n- Unauthorized access to draft/provisional/revision content via token replay.\n- Stealthy one-click exploitation against logged-in editors/admins.\n- No dependency on forwarded-host poisoning.\n\n---",
  "id": "GHSA-vg3j-hpm9-8v5v",
  "modified": "2026-09-02T13:35:21Z",
  "published": "2026-03-10T18:22:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/security/advisories/GHSA-vg3j-hpm9-8v5v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-29113"
    },
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/commit/6a88468dc35a27cccc8fef254f415a447d4a07cc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/craftcms/cms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Craft CMS has a potential information disclosure vulnerability in preview tokens"
}



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