AC.L2-3.5.5[a] — Identification & Authentication (Identifier Reuse)Domain: Identification & Authentication (IA) | Practice: IA.L2-3.5.5 | Objective ID: 3.5.5[a] | Source: NIST SP 800-171 Rev. 2 / CMMC 2.0 Level 2 | Assessment Objective: A time period for which identifiers will not be reused is defined. |
Executive Summary (For Leadership and the Board)
CMMC objective AC.L2-3.5.5[a] sits inside the Identification & Authentication domain (IA.L2-3.5.5 — Identifier Reuse) and reads: A time period for which identifiers will not be reused is defined.. Define a minimum period (often 2+ years) before deactivated user or device identifiers can be reassigned. Premature reuse creates confusion in audit trails and access control. For organizations that handle Controlled Unclassified Information (CUI), this objective is part of the foundation that every downstream control depends on.
Under DFARS 252.204-7012, AC.L2-3.5.5[a] will be evaluated during a full third-party CMMC Level 2 assessment, Joint Surveillance Voluntary Assessment, or formal certification gating DoD CUI contract awards. Leadership and the board should be asking: Who owns this objective? When was it last reviewed? Where is the evidence stored? And what is our remediation plan if a C3PAO flags a gap? Failing this objective in isolation may be POA&M-able under CMMC 2.0; failing it in conjunction with related objectives in the same practice is typically not.