CVE-2026-41669

Admidio is an open-source user management solution. Prior to version 5.0.9, the Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones. This issue has been patched in version 5.0.9.

Admidio is an open-source user management solution. Prior to version 5.0.9, the Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones. This issue has been patched in version 5.0.9.

Summary

The Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones.

Details

The validateSignature() method at src/SSO/Service/SAMLService.php:355 has three possible return paths:

// Line 355-392
public function validateSignature(SAMLClient $client, SamlMessage $message, bool $required = false): bool|string {
    global $gL10n;
    $certPem = $client->getValue('smc_x509_certificate');
    if (!$certPem) {
        if ($required) {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_KEY_MISSING'); // Returns STRING, not throw
        } else {
            return false;
        }
    }
    // ...
    $signatureReader = $message->getSignature();
    if (is_null($signatureReader)) {
        if ($required) {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_MISSING'); // Returns STRING, not throw
        } else {
            return false;
        }
    }
    try {
        $ok = $signatureReader->validate($key);
        if ($ok) {
            return true;
        } else {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_FAILED'); // Returns STRING, not throw
        }
    } catch (Exception $ex) {
        return $gL10n->get('SYS_SSO_SAML_SIGNATURE_FAILED'); // Returns STRING, not throw
    }
}

Both call sites discard the return value entirely:

// Line 416-419 in handleSSORequest()
// Validate signatures. Will throw an exception    <-- INCORRECT COMMENT
if ($client->getValue('smc_require_auth_signed') || $client->getValue('smc_validate_signatures')) {
    $this->validateSignature($client, $request, $client->getValue('smc_require_auth_signed'));
    // Return value discarded — execution continues regardless of validation result
}

// Line 611-614 in handleSLORequest()
// Validate signatures. Will throw an exception    <-- INCORRECT COMMENT
if ($client->getValue('smc_require_auth_signed') || $client->getValue('smc_validate_signatures')) {
    $this->validateSignature($client, $request, $client->getValue('smc_require_auth_signed'));
    // Return value discarded — execution continues regardless of validation result
}

SSO exploitation path (for already-logged-in users):

1. modules/sso/index.php:92 routes to handleSSORequest()
2. Line 403: receiveMessage() parses SAML binding directly from HTTP GET/POST — no authentication required
3. Line 408-409: Entity ID extracted from the forged request's Issuer element, client config loaded
4. Line 417-419: Signature validation called but return value discarded — flow continues
5. Line 421: $gValidLogin is true for logged-in users, so login form is skipped
6. Lines 438-580: SAML Response built with user's real attributes (login, name, email, roles) and sent to the AssertionConsumerServiceURL from the forged request

SLO exploitation path:

1. modules/sso/index.php:94 routes to handleSLORequest()
2. Line 613: Signature validation discarded
3. Lines 621-629: User's session is deleted from the database and $gCurrentSession->logout() is called

PoC

# Prerequisites:
# - Admidio instance with SAML SSO enabled (sso_saml_enabled=1)
# - At least one registered SAML SP client with smc_require_auth_signed=true
# - A user with an active session (e.g., admin browsing the Admidio panel)

# 1. Generate an unsigned AuthnRequest impersonating a registered SP:
AUTHN_REQUEST=$(python3 -c "
import base64, zlib
req = '<samlp:AuthnRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\"…

Admidio is an open-source user management solution. Prior to version 5.0.9, the Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones. This issue has been patched in version 5.0.9.

Admidio is an open-source user management solution. Prior to version 5.0.9, the Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones. This issue has been patched in version 5.0.9.

Summary

The Admidio SAML Identity Provider implementation discards the return value of its validateSignature() method at both call sites (handleSSORequest() line 418 and handleSLORequest() line 613). The method returns error strings on failure rather than throwing exceptions, but the developer believed it would throw (per comments on lines 416 and 611). This means the smc_require_auth_signed configuration option is completely ineffective — unsigned or invalidly-signed SAML AuthnRequests and LogoutRequests are processed identically to properly signed ones.

Details

The validateSignature() method at src/SSO/Service/SAMLService.php:355 has three possible return paths:

// Line 355-392
public function validateSignature(SAMLClient $client, SamlMessage $message, bool $required = false): bool|string {
    global $gL10n;
    $certPem = $client->getValue('smc_x509_certificate');
    if (!$certPem) {
        if ($required) {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_KEY_MISSING'); // Returns STRING, not throw
        } else {
            return false;
        }
    }
    // ...
    $signatureReader = $message->getSignature();
    if (is_null($signatureReader)) {
        if ($required) {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_MISSING'); // Returns STRING, not throw
        } else {
            return false;
        }
    }
    try {
        $ok = $signatureReader->validate($key);
        if ($ok) {
            return true;
        } else {
            return $gL10n->get('SYS_SSO_SAML_SIGNATURE_FAILED'); // Returns STRING, not throw
        }
    } catch (Exception $ex) {
        return $gL10n->get('SYS_SSO_SAML_SIGNATURE_FAILED'); // Returns STRING, not throw
    }
}

Both call sites discard the return value entirely:

// Line 416-419 in handleSSORequest()
// Validate signatures. Will throw an exception    <-- INCORRECT COMMENT
if ($client->getValue('smc_require_auth_signed') || $client->getValue('smc_validate_signatures')) {
    $this->validateSignature($client, $request, $client->getValue('smc_require_auth_signed'));
    // Return value discarded — execution continues regardless of validation result
}

// Line 611-614 in handleSLORequest()
// Validate signatures. Will throw an exception    <-- INCORRECT COMMENT
if ($client->getValue('smc_require_auth_signed') || $client->getValue('smc_validate_signatures')) {
    $this->validateSignature($client, $request, $client->getValue('smc_require_auth_signed'));
    // Return value discarded — execution continues regardless of validation result
}

SSO exploitation path (for already-logged-in users):

1. modules/sso/index.php:92 routes to handleSSORequest()
2. Line 403: receiveMessage() parses SAML binding directly from HTTP GET/POST — no authentication required
3. Line 408-409: Entity ID extracted from the forged request's Issuer element, client config loaded
4. Line 417-419: Signature validation called but return value discarded — flow continues
5. Line 421: $gValidLogin is true for logged-in users, so login form is skipped
6. Lines 438-580: SAML Response built with user's real attributes (login, name, email, roles) and sent to the AssertionConsumerServiceURL from the forged request

SLO exploitation path:

1. modules/sso/index.php:94 routes to handleSLORequest()
2. Line 613: Signature validation discarded
3. Lines 621-629: User's session is deleted from the database and $gCurrentSession->logout() is called

PoC

# Prerequisites:
# - Admidio instance with SAML SSO enabled (sso_saml_enabled=1)
# - At least one registered SAML SP client with smc_require_auth_signed=true
# - A user with an active session (e.g., admin browsing the Admidio panel)

# 1. Generate an unsigned AuthnRequest impersonating a registered SP:
AUTHN_REQUEST=$(python3 -c "
import base64, zlib
req = '<samlp:AuthnRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\"…