Description
CIE.AspNetCore.Authentication is an AspNetCore Remote Authenticator for CIE 3.0. Authentication using Spid and CIE is based on the SAML2 standard which provides two entities: 1. Identity Provider (IDP): the system that authenticates users and provides identity information (SAML affirmation) to the Service Provider, in essence, is responsible for the management of the credentials and identity of users; 2. Service Provider (SP): the system that provides a service to the user and relies on the Identity Provider to authenticate the user, receives SAML assertions from the IdP to grant access to resources. The library cie-aspnetcore refers to the second entity, the SP, and implements the validation logic of SAML assertions within SAML responses. In affected versions there is no guarantee that the first signature refers to the root object, it follows that if an attacker injects an item signed as the first element, all other signatures will not be verified. The only requirement is to have an XML element legitimately signed by the IdP, a condition that is easily met using the IdP's public metadata. An attacker could create an arbitrary SAML response that would be accepted by SPs using vulnerable SDKs, allowing him to impersonate any Spid and/or CIE user. This issue has been addressed in version 2.1.0 and all users are advised to upgrade. There are no known workarounds for this vulnerability.
EPSS Score:
0%
Comprehensive Technical Analysis of EUVD-2025-4791
1. Vulnerability Assessment and Severity Evaluation
The vulnerability described in EUVD-2025-4791 affects the CIE.AspNetCore.Authentication library, which is used for authenticating users via the SAML2 standard in AspNetCore applications. The core issue lies in the validation logic of SAML assertions within SAML responses. Specifically, the library does not ensure that the first signature in the SAML response refers to the root object. This flaw allows an attacker to inject a signed XML element as the first element, bypassing the verification of subsequent signatures.
Severity Evaluation:
- CVSS Base Score: 9.1
- CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
The high base score indicates a critical vulnerability due to the ease of exploitation (low complexity, no privileges required, no user interaction needed) and the significant impact on confidentiality and integrity.
2. Potential Attack Vectors and Exploitation Methods
Attack Vectors:
- SAML Response Tampering: An attacker can craft a malicious SAML response where the first element is legitimately signed by the Identity Provider (IdP). This element can be obtained from the IdP's public metadata.
- Impersonation: By injecting a signed element, the attacker can create an arbitrary SAML response that will be accepted by the Service Provider (SP), allowing the attacker to impersonate any Spid and/or CIE user.
Exploitation Methods:
- Obtain Legitimate Signature: The attacker needs to obtain a legitimately signed XML element from the IdP's public metadata.
- Craft Malicious SAML Response: The attacker constructs a SAML response with the signed element as the first item, followed by arbitrary data.
- Send Malicious Response: The attacker sends the crafted SAML response to the vulnerable SP, which accepts it due to the flawed validation logic.
3. Affected Systems and Software Versions
Affected Software:
cie-aspnetcorelibrary versions prior to 2.1.0.
Affected Systems:
- Any AspNetCore application using the
CIE.AspNetCore.Authenticationlibrary for SAML2-based authentication with Spid and CIE.
4. Recommended Mitigation Strategies
Immediate Mitigation:
- Upgrade: Upgrade to version 2.1.0 or later of the
cie-aspnetcorelibrary, which addresses the vulnerability.
Long-Term Mitigation:
- Regular Updates: Ensure that all libraries and dependencies are regularly updated to the latest versions.
- Code Review: Conduct thorough code reviews and security audits of authentication mechanisms.
- Monitoring: Implement monitoring and alerting for suspicious authentication activities.
5. Impact on European Cybersecurity Landscape
The vulnerability poses a significant risk to European organizations relying on the CIE.AspNetCore.Authentication library for user authentication, particularly those using Spid and CIE for identity management. Successful exploitation could lead to unauthorized access to sensitive information and services, compromising user data and trust in digital identity systems.
6. Technical Details for Security Professionals
Vulnerability Details:
- The flaw resides in the SAML assertion validation logic, where the library does not verify that the first signature corresponds to the root object.
- An attacker can exploit this by injecting a signed XML element as the first item in the SAML response, bypassing subsequent signature verifications.
Exploitation Steps:
- Retrieve Signed Element: Obtain a legitimately signed XML element from the IdP's public metadata.
- Construct SAML Response: Create a SAML response with the signed element as the first item, followed by arbitrary data.
- Send Response: Transmit the crafted SAML response to the vulnerable SP.
Detection and Response:
- Log Analysis: Review authentication logs for unusual patterns or failed authentication attempts.
- Intrusion Detection: Implement intrusion detection systems (IDS) to monitor for suspicious SAML response patterns.
- Incident Response: Develop an incident response plan to address potential breaches, including steps for containment, eradication, and recovery.
References:
By addressing this vulnerability promptly and implementing robust security measures, organizations can mitigate the risk of unauthorized access and maintain the integrity of their authentication systems.