^{CVE-2023-20270:}A vulnerability in Cisco Firepower Threat Defense (FTD) Software allows remote attackers to bypass policies or cause denial of service through crafted SMB traffic.

Overview

This vulnerability exists in the Cisco Firepower Threat Defense (FTD) Software's handling of SMB traffic through the Snort 3 detection engine. The core issue is inadequate error-checking in the interaction between the SMB protocol preprocessor and the Snort 3 engine. When exploited, this vulnerability can lead to two significant security impacts: policy bypass that could allow unauthorized traffic through the firewall, or a denial of service condition where the Snort process reloads, temporarily disrupting inspection capabilities. Since the attack requires only the ability to send network traffic to the affected device, it can be executed remotely without authentication, making it particularly dangerous in internet-facing deployments.

Remediation

Organizations should apply the appropriate patches provided by Cisco as soon as possible. If immediate patching is not possible, consider implementing the following mitigations:

1. Monitor for suspicious SMB traffic targeting your Cisco FTD devices
2. Implement network segmentation to limit exposure of affected devices
3. Apply access control lists to restrict SMB traffic to only necessary sources
4. Consider temporarily increasing monitoring of Snort process restarts as a potential indicator of exploitation attempts
5. Review Cisco's security advisory (cisco-sa-ftd-smbsnort3-dos-pfOjOYUV) for specific version information and patching guidance

References

1. Cisco Security Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-smbsnort3-dos-pfOjOYUV
2. Cisco Firepower Threat Defense Documentation: https://www.cisco.com/c/en/us/products/security/firepower-ngfw/index.html
3. SMB Protocol Security Best Practices: Consider limiting SMB traffic across security boundaries where possible
4. Snort 3 Documentation: https://www.snort.org/snort3