A recently exposed vulnerability in the Cisco Secure Client security software allows hackers to conduct carriage return line feed (CRLF) injection attacks without authentication. This means private and sensitive information may be at risk if a user clicks on a link created by a cybercriminal. Specifically, the security gap comes from a lack of thorough validation for user input.

Cisco Advisory

Exploit Details

In the event that the vulnerability is exploited, an attacker could gain unauthorized access to a legitimate user's SAML token. With the token, the attacker can set up a VPN session remotely and potentially access the individual services and hosts behind the VPN headend. To access these services successfully, however, the attacker would need additional permissions.

The code snippet below demonstrates the structure of the malicious payload used to exploit this vulnerability:


Preventative Measures

To mitigate the risk associated with this vulnerability, Cisco has released a set of patches. Users should install these patches promptly and stay apprised of future updates from Cisco. Furthermore, exercising caution when clicking on unfamiliar links can help avoid exposure to such attacks.

In addition to the patches, Cisco offers guidelines for identifying and securing systems that may be vulnerable:
Cisco Guide


CVE-2024-20337 reports a vulnerability tied to the SAML authentication process in the Cisco Secure Client, making it possible for remote cybercriminals to conduct CRLF injection attacks without authentication. Users must take the necessary precautions as outlined above, such as installing patches and being cautious when clicking unknown links. It is crucial to stay informed about future updates from Cisco to avoid compromising security due to this vulnerability.


Published on: 03/06/2024 17:15:09 UTC
Last modified on: 03/07/2024 13:52:27 UTC