Comprehensive and Detailed In-Depth Explanation:

CMMC practice RA.L2-3.11.2 – Vulnerability Scans requires organizations to "scan for vulnerabilities in organizational systems and applications periodically and when new vulnerabilities affecting those systems and applications are identified." The OSC’s process includes robust system scanning, but the lack of source code scanning for custom applications is a gap, as vulnerabilities in code can persist into production if not addressed at the development stage. While the practice doesn’t explicitly mandate source code scanning, it’s a critical component of a comprehensive vulnerability management program, especially for a software development OSC handling CUI.

Among the options,performing periodic penetration testing and code reviews (C)is the most appropriate compensating control for the absence of automated source code scanning. Penetration testing simulates attacks to identify exploitable vulnerabilities in the application, while manual code reviews can uncover issues missed by system scans (e.g., logic flaws, insecure coding practices). This directly addresses the gap by ensuring vulnerabilities in custom code are identified and mitigated, aligning with the intent of RA.L2-3.11.2 to manage vulnerabilities effectively.

Option A (Web Application Firewalls):WAFs can mitigate some runtime exploits but don’t identify or fix underlying code vulnerabilities, making them a partial solution that doesn’t fully compensate for the lack of scanning.

Option B (Increase Scan Frequency):More frequent system scans won’t detect code-level issues, as they target deployed systems, not source code.

Option D (Secure Coding Standards):While proactive and valuable, standards prevent future issues but don’t address existing vulnerabilities in current code, lacking the immediate compensatory effect needed.

The CMMC Assessment Guide encourages compensating controls that directly tackle identified gaps, and penetration testing combined with code reviews is a recognized industry practice (e.g., NIST SP 800-53 CA-8, RA-5) for mitigating unaddressed code vulnerabilities.

Extract from Official CMMC Documentation:

CMMC Assessment Guide Level 2 (v2.0), RA.L2-3.11.2: "Scan for vulnerabilities in systems and applications; remediation or mitigation required for identified issues."

NIST SP 800-171A, 3.11.2: "Examine scanning processes; compensating controls like penetration testing can address gaps in vulnerability identification."

Discussion Note: "Organizations may use additional methods (e.g., penetration testing) to identify vulnerabilities not covered by automated scans."

Resources:

https://dodcio.defense.gov/Portals/0/Documents/CMMC/AG_Level2_MasterV2.0_FINAL_202112016_508.pdf