{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "781cebf19406c9db4c769f35a78c991326393b98"
            },
            {
              "fixed": "979cfc1bcd6399afa0477cbc6f7457a211f26cdc"
            }
          ],
          "repo": "https://github.com/misskey-dev/misskey",
          "type": "GIT"
        }
      ]
    },
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "12.0.0"
              },
              {
                "fixed": "2025.4.1"
              }
            ]
          },
          "events": [
            {
              "introduced": "781cebf19406c9db4c769f35a78c991326393b98"
            },
            {
              "fixed": "979cfc1bcd6399afa0477cbc6f7457a211f26cdc"
            }
          ],
          "repo": "https://github.com/syuilo/misskey",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-3p2w-xmv5-jm95"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-116",
      "CWE-20"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46340.json"
  },
  "details": "Misskey is an open source, federated social media platform. Starting in version 12.0.0 and prior to version 2025.4.1, due to an oversight in the validation performed in `UrlPreviewService` and `MkUrlPreview`, it is possible for an attacker to inject arbitrary CSS into the `MkUrlPreview` component. `UrlPreviewService.wrap` falls back to returning the original URL if it's using a protocol that is likely to not be understood by Misskey, IE something other than `http` or `https`. This both can de-anonymize users and_allow further attacks in the client. Additionally, `MkUrlPreview` doesn't escape CSS when applying a `background-image` property, allowing an attacker to craft a URL that applies arbitrary styles to the preview element. Theoretically, an attacker can craft a CSS injection payload to create a fake error message that can deceive the user into giving away their credentials or similar sensitive information. Version 2025.4.1 contains a patch for the issue.",
  "id": "CVE-2025-46340",
  "modified": "2026-04-01T23:10:35.110977331Z",
  "published": "2025-05-05T18:35:37.852Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46340.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/misskey-dev/misskey/security/advisories/GHSA-3p2w-xmv5-jm95"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-46340"
    },
    {
      "type": "FIX",
      "url": "https://github.com/misskey-dev/misskey/commit/d10fdfe9738b17a9d81037c031b40a2cc4cb8038"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Misskey CSS Style Injection Vulnerability In `MkUrlPreview`"
}