Description
A flaw has been identified in the SAML authentication process within Cisco Secure Client, potentially enabling an unauthorized remote attacker to carry out a CRLF injection attack against a user. This vulnerability stems from inadequate validation of input provided by users.
By leveraging this vulnerability, an attacker could manipulate a user into clicking on a malicious link while initiating a VPN session. This successful exploitation could lead to the execution of arbitrary script code in the user’s browser or unauthorized access to sensitive browser-based data, including a valid SAML token.
Subsequently, the attacker could utilize this token to establish a remote access VPN session with the privileges associated with the compromised user account. It’s important to note that accessing individual hosts and services behind the VPN headend would still require additional authentication credentials for successful entry.
Severity
Base Score: 8.2 HIGH
Affected Platforms and Software:
| Affected Platform | Affected Software |
| Secure Client for Linux Secure Client for macOS Secure Client for Windows | Version 5.0 Version 5.1 Version 4.1 |
Threat:
- Execution of arbitrary code
- Breach of data confidentiality
An attacker might take advantage of this vulnerability by coaxing a user into clicking on a carefully crafted link during the setup of a VPN session. If the exploit is successful, it could grant the attacker the ability to run arbitrary script code directly in the user’s browser or gain access to critical, browser-dependent data, which could include a legitimate SAML token. With possession of this token, the attacker could subsequently initiate a remote access VPN session, assuming the privileges and access rights of the impacted user.
Mitigation Plan:
| Cisco Secure Client Release | First Fixed Release |
| Earlier than 4.10.04065 | Not vulnerable. |
| 4.10.04065 and later | 4.10.08025 |
| 5.0 | Migrate to a fixed release. |
| 5.1 | 5.1.2.42 |
Additional Mitigation Strategies
Here are some mitigation strategies based on the vulnerability described:
1. Implement Strict Input Validation:
Ensure that all user-supplied input, especially during the authentication process, undergoes rigorous validation to detect and reject any malicious or unexpected characters, including carriage return line feed (CRLF) sequences.
2. User Awareness and Training:
Educate users about the risks associated with clicking on untrusted or suspicious links, especially while initiating VPN sessions. Encourage them to exercise caution and verify the authenticity of URLs before clicking on them.
3. Enhance VPN Security Measures:
Improve the security of the VPN infrastructure by implementing multi-factor authentication (MFA) for VPN sessions. This adds an extra layer of protection by requiring users to provide additional authentication factors beyond just a username and password.
4. Regular Security Audits and Penetration Testing:
Conduct frequent security audits and penetration testing to identify and address vulnerabilities in the SAML authentication process and other critical systems. This helps in proactively identifying and mitigating potential threats.
5. Patch and Update Systems:
Ensure that all systems, including VPN servers and client applications, are regularly patched and updated with the latest security patches and fixes. This helps close known security vulnerabilities that could be exploited by attackers.
6. Implement Security Controls in Web Browsers:
Configure web browsers with appropriate security controls, such as content filtering, script blocking, and sandboxing, to mitigate the risk of executing arbitrary script code from malicious links.
7. Monitor and Analyze Network Traffic:
Deploy intrusion detection systems (IDS) and intrusion prevention systems (IPS) to monitor and analyze network traffic for any suspicious or anomalous activities. Set up alerts for CRLF injection attempts or other potential attack patterns.
8. Access Controls and Privilege Management:
Enforce strict access controls and privilege management policies to limit the impact of successful attacks. Ensure that users only have access to the resources and privileges necessary for their roles and responsibilities.
By implementing these mitigation strategies, organizations can significantly reduce the risk of exploitation through CRLF injection attacks during VPN session establishment and enhance their overall network security posture.
References :
| Avis de sécurité Cisco Cisco Secure Client Carriage Return Line Feed Injection Vulnerability Mitre CVE-2024-20337 CVE – CVE-2024-20337 (mitre.org) NIST CVE-2024-20337 NVD – CVE-2024-20337 (nist.gov) |