GHSA-P279-5WCV-45VQ

Vulnerability from github – Published: 2026-10-07 18:05 – Updated: 2026-10-07 18:05
VLAI
Summary
Kunstmaan CMS: MediaBundle extension blacklist bypass allows authenticated administrators to upload executable PHP files leading to remote code execution
Details

Summary

The MediaBundle blocks dangerous upload extensions with a blacklist that was matched case-sensitively, while the stored filename was lowercased afterwards. A file uploaded as webshell.pHp therefore bypassed the blacklist and was written to the web-accessible upload directory as webshell.php, where the web server executed it. Any authenticated backend user with access to the media section could obtain remote code execution.

Details

FileHandler::getFilePath() rewrote blacklisted extensions to .txt using a case-sensitive regex, and only then lowercased the extension when building the stored name — so the check ran against the attacker-controlled casing and the normalisation happened after it.

Two further weaknesses contributed:

  • The default blacklist contained only php and htaccess, leaving other server-executable extensions (phtml, php5, phar, shtml, cgi, …) unblocked regardless of casing.
  • Configured blacklist values were interpolated into the regex unescaped.

Impact

An authenticated user with access to the admin media section can upload a file that the web server executes as PHP. The uploaded file is reachable over HTTP without authentication, giving arbitrary code execution as the web server user.

Patches

Fixed in kunstmaan/media-bundle 7.3.2. The extension is now normalised before it is checked and compared with in_array(); the default blacklist is expanded to the full set of server-executable extensions; and a new opt-in allowed_extensions option allows projects to enforce a strict allow-list.

Note that the patch does not rename files already stored on disk. Sites should audit their media upload directory for existing files with an executable extension.

Workarounds

If you cannot upgrade, configure the web server to refuse to execute scripts in the media upload directory (for example a location block in nginx or php_flag engine off in Apache).

Severity
7.2 (High)
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "kunstmaan/media-bundle"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "kunstmaan/bundles-cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-104890"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-434"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-07T18:05:38Z",
    "nvd_published_at": "2026-10-05T16:17:06Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe MediaBundle blocks dangerous upload extensions with a blacklist that was matched\ncase-sensitively, while the stored filename was lowercased afterwards. A file uploaded\nas `webshell.pHp` therefore bypassed the blacklist and was written to the web-accessible\nupload directory as `webshell.php`, where the web server executed it. Any authenticated\nbackend user with access to the media section could obtain remote code execution.\n\n### Details\n\n`FileHandler::getFilePath()` rewrote blacklisted extensions to `.txt` using a\ncase-sensitive regex, and only then lowercased the extension when building the stored\nname \u2014 so the check ran against the attacker-controlled casing and the normalisation\nhappened after it.\n\nTwo further weaknesses contributed:\n\n* The default blacklist contained only `php` and `htaccess`, leaving other\n  server-executable extensions (`phtml`, `php5`, `phar`, `shtml`, `cgi`, \u2026) unblocked\n  regardless of casing.\n* Configured blacklist values were interpolated into the regex unescaped.\n\n### Impact\n\nAn authenticated user with access to the admin media section can upload a file that the\nweb server executes as PHP. The uploaded file is reachable over HTTP without\nauthentication, giving arbitrary code execution as the web server user.\n\n### Patches\n\nFixed in kunstmaan/media-bundle 7.3.2. The extension is now normalised before it is\nchecked and compared with `in_array()`; the default blacklist is expanded to the full\nset of server-executable extensions; and a new opt-in `allowed_extensions` option allows\nprojects to enforce a strict allow-list.\n\nNote that the patch does not rename files already stored on disk. Sites should audit\ntheir media upload directory for existing files with an executable extension.\n\n### Workarounds\n\nIf you cannot upgrade, configure the web server to refuse to execute scripts in the\nmedia upload directory (for example a `location` block in nginx or `php_flag engine off`\nin Apache).",
  "id": "GHSA-p279-5wcv-45vq",
  "modified": "2026-10-07T18:05:38Z",
  "published": "2026-10-07T18:05:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kunstmaan/KunstmaanBundlesCMS/security/advisories/GHSA-p279-5wcv-45vq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-104890"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Kunstmaan/KunstmaanBundlesCMS/commit/1bbdfdeac8e7e91506b1a9271360b9b68d7690d3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kunstmaan/KunstmaanBundlesCMS"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Kunstmaan/KunstmaanBundlesCMS/releases/tag/7.3.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Kunstmaan CMS: MediaBundle extension blacklist bypass allows authenticated administrators to upload executable PHP files leading to remote code execution"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.