03.13.15: Session Authenticity

To meet the 03.13.15: session authenticity requirement, you must ensure every authenticated session (user, admin, service, and API) is protected against hijacking and impersonation, and that session tokens cannot be forged, replayed, or reused outside their intended context. Operationally, this means strong session token design, secure transport, sensible timeouts, and monitoring that detects suspicious session behavior. ¹

Key takeaways:

• Treat session tokens as high-value credentials: generate them securely, bind them to context, and protect them in transit and at rest. ¹
• Implement controls that prevent hijacking (TLS, secure cookie flags, token rotation, timeout, re-auth for sensitive actions). ¹
• Keep assessor-ready evidence: configurations, standards, and logs showing the controls operate across web, VPN, remote admin, and APIs. ¹

“Session authenticity” is where many otherwise solid identity programs fail in practice. You can have strong MFA and still lose control of an account if an attacker steals or replays a valid session token, abuses a long-lived refresh token, or exploits weak cookie settings. Requirement 03.13.15: session authenticity requirement pushes you to address that gap: authenticated sessions must remain trustworthy from creation to termination, across browsers, thick clients, remote access, and API-to-API calls that touch CUI environments. ¹

For a Compliance Officer or GRC lead, the fastest path is to translate “session authenticity” into a short set of non-negotiable technical and operational standards: how sessions are created, how they are protected, how long they last, how they are revoked, and how you detect anomalies. Then you prove coverage with system configurations and objective evidence from your identity provider, web stack, endpoint management, VPN/VDI tooling, and application gateways. ¹

This page gives requirement-level implementation guidance you can hand to engineering, IAM, and security operations, plus the audit artifacts you should collect on a recurring basis so you are not rebuilding evidence during an assessment.

Regulatory text

Excerpt (as provided): “NIST SP 800-171 Rev. 3 requirement 03.13.15 (Session Authenticity).” ¹

Operator interpretation: You must implement controls that maintain the integrity and legitimacy of authenticated sessions. An assessor will expect that session identifiers (cookies, tokens, SSO assertions, refresh tokens, API tokens) are generated securely, transmitted securely, protected from client-side theft, expire appropriately, and can be revoked. They will also expect coverage across common session entry points: interactive user sessions, administrative sessions, remote access sessions, and programmatic/API sessions that access systems processing CUI. ¹

Plain-English interpretation (what the requirement is really asking)

If a session exists, you should be able to answer: “Why do we trust this session right now?” Session authenticity means the session stays bound to the authenticated principal and cannot be easily taken over by someone else.

Practically, you are defending against:

• Session hijacking (stolen cookie/token, malware, phishing-based token theft, device compromise)
• Session fixation (attacker sets a known session ID before login)
• Replay and reuse (token captured and replayed from another device/location)
• Weak token issuance (predictable tokens, improper signing, poor entropy)
• Overly long sessions (stolen tokens remain valid too long)
• Incomplete logout/revocation (user “logs out” but token stays valid)

Who it applies to (entity and operational context)

Applies to organizations operating nonfederal systems that handle CUI, commonly federal contractors and their supporting environments where CUI is processed, stored, or transmitted. ¹

Operationally, scope it to:

• Identity providers / SSO (session lifetime, token signing, conditional access)
• Web apps handling CUI (cookies, sessions, CSRF protections)
• APIs that access CUI (access tokens, refresh tokens, mTLS where used)
• Admin interfaces (privileged session controls, re-auth, tighter timeouts)
• Remote access (VPN, VDI, ZTNA session policies)
• Third-party connections into CUI environments (support tools, managed services)

What you actually need to do (step-by-step)

1) Define the session types and session “assets” you issue

Create a simple inventory table per system in scope:

• Session mechanism (server-side session ID, JWT access token, SAML session, OAuth refresh token)
• Storage location (HTTP-only cookie, local storage, client cache, device keychain)
• Issuer (app, IdP, gateway)
• Validation point (app server, API gateway, reverse proxy)
• Revocation method (token blacklist, introspection, session store deletion)

Output artifact: “Session Mechanisms Inventory” attached to your SSP or system security documentation. ¹

2) Standardize secure session issuance (prevent forgery and fixation)

Set a baseline standard your teams must follow:

• Use cryptographically secure random session IDs or properly signed tokens.
• Regenerate session identifiers on authentication events (login, privilege elevation).
• Do not accept externally supplied session IDs pre-auth (fixation defense).

Evidence: secure coding standard excerpts; application framework configuration; code review checklist entries; change tickets showing adoption.

3) Protect sessions in transit and at the endpoint

Minimum operational expectations:

• Encrypt session traffic end-to-end using TLS.
• For browser sessions: set cookies to Secure and HttpOnly, and apply an appropriate SameSite policy.
• Avoid storing bearer tokens in browser local storage for CUI apps unless you have compensating controls and documented rationale.
• For thick clients: store tokens in OS-protected key storage, not plaintext config files.

Evidence: TLS configuration output; web server/app framework cookie settings; secure storage design notes; configuration screenshots or exported policies.

4) Bind sessions to context where feasible

Session authenticity improves when a stolen token is less useful:

• Use device-aware and risk-aware access policies in your IdP (device posture, location, impossible travel rules if supported).
• Consider binding sessions to client properties (token audience, issuer, nonce, and other standard claims) and validate them at every request.
• For high-risk admin access, require step-up authentication for sensitive actions.

Evidence: IdP conditional access policies; privileged access policy documents; application token validation logic documented in an engineering standard.

5) Implement timeouts, rotation, and revocation that actually work

Define session lifecycle rules:

• Idle timeout and absolute lifetime for interactive sessions.
• Short-lived access tokens with refresh tokens protected and rotated (where OAuth is used).
• Immediate revocation on password reset, MFA reset, HR termination, or suspected compromise.
• Centralized logout that invalidates server-side sessions and refresh tokens, not just a UI redirect.

Evidence: IdP session settings export; OAuth client configuration; runbook for account compromise; test records showing tokens become invalid after revocation.

6) Monitor for session anomalies and respond

Session authenticity is not only preventative. You also need detection:

• Alert on unusual session creation patterns (new device + privileged account, impossible travel where supported).
• Alert on token replay indicators (same token used from different IPs rapidly, concurrent sessions beyond policy).
• Log authentication and session events with enough detail to investigate.

Evidence: SIEM alert definitions; sample alerts; authentication logs; incident response tickets showing triage steps.

7) Validate coverage in assessment-friendly tests

Run targeted tests that map cleanly to the requirement:

• Attempt session fixation in a test environment.
• Confirm cookies have Secure/HttpOnly/SameSite where expected.
• Confirm tokens expire and are rejected after logout and after credential reset.
• Confirm privileged actions trigger re-auth where required.

Evidence: test plan, test results, and remediation tickets tied to the system.

Required evidence and artifacts to retain

Keep these in a single control folder mapped to the 03.13.15: session authenticity requirement:

• Session mechanisms inventory per in-scope system
• IdP session policy exports (lifetime, conditional access, token settings)
• Web/app configuration evidence (cookie flags, session regen settings, CSRF settings if applicable)
• API gateway or auth service configuration (token validation, audience/issuer checks)
• Revocation and compromise runbooks (including HR offboarding triggers)
• Logging and monitoring evidence (event types collected, alert rules, sample investigations)
• Change management records showing periodic review and updates

Daydream can help by turning this into a recurring evidence checklist and mapping the artifacts to the requirement so audits don’t become a screenshot hunt. ¹

Common exam/audit questions and hangups

Assessors and internal auditors tend to focus on these specifics:

• “Show me where session lifetimes are configured for your IdP and for this application.”
• “What happens to sessions after a user changes their password or is terminated?”
• “Do admin sessions have stricter rules than standard user sessions?”
• “Where are tokens stored on endpoints, and what prevents theft?”
• “Can you prove tokens are rejected after logout or revocation?”
• “Do you log session creation and session termination events with user identity and source context?”

Hangup: teams document MFA well but cannot prove session termination and revocation behavior across apps.

Frequent implementation mistakes and how to avoid them

1. Relying on MFA alone

• Fix: explicitly control session lifetime, token theft protections, and revocation. MFA is the front door, sessions are the hallway.

2. Long-lived refresh tokens without rotation

• Fix: enable rotation where supported, and treat refresh tokens as privileged secrets with strong storage and strict revocation.

3. Logout that doesn’t invalidate anything

• Fix: implement server-side invalidation (session store delete, token revocation, introspection deny) and test it.

4. Inconsistent cookie settings across apps

• Fix: publish a cookie/session standard and add a deployment gate (SAST/DAST checks or config validation) for CUI apps.

5. No evidence trail

• Fix: define an evidence owner, collect exports on a schedule, and keep “before/after” records for major changes.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so this page does not cite specific actions.

Risk-wise, session authenticity failures are a common path from “initial access” to “data access” because a valid session often bypasses repeated authentication checks. In a CUI environment, a hijacked session can mean unauthorized access to CUI without tripping password or MFA controls, which drives incident scope, reporting obligations, and contractual risk. ¹

Practical execution plan (30/60/90 days)

First 30 days (stabilize scope and set baselines)

• Identify in-scope systems that handle CUI and list their session mechanisms.
• Export IdP session policies and document current session lifetimes and conditional access rules.
• Publish a one-page “Session Standard” for CUI apps: token storage rules, cookie flags, regen-on-auth requirement, and revocation expectations.
• Choose initial evidence set and assign owners (IAM, app platform, SecOps).

By 60 days (implement and prove revocation + timeouts)

• Implement or tighten session regeneration, cookie flags, and token validation checks across priority apps.
• Configure revocation triggers (termination, password reset, compromise) and test that sessions die as expected.
• Implement baseline session anomaly alerts and confirm logs contain user, device/IP context, and timestamp.

By 90 days (operationalize and make it repeatable)

• Expand coverage to remaining apps and APIs in scope, including third-party integrations that reach CUI systems.
• Add CI/CD or configuration checks to prevent regressions (cookie settings, token lifetime policies).
• Run a tabletop focused on token theft/session hijack, then capture improvements as tracked action items.
• Move evidence collection into a recurring workflow (Daydream or your existing GRC system) tied to audit calendars. ¹

Frequently Asked Questions

Does 03.13.15 require MFA?

The requirement is about session authenticity, not a specific authentication factor. MFA helps, but you still need session controls like secure token handling, expiration, and revocation. ¹

Are API tokens and service accounts in scope for session authenticity?

Yes if they create authenticated sessions or tokens used to access CUI systems. Treat OAuth access/refresh tokens and long-lived API keys as session artifacts with lifecycle controls and revocation. ¹

What evidence is strongest for an assessor?

Policy alone is weak. Provide configuration exports (IdP, app framework, gateway) plus test results showing tokens expire and are invalid after logout and credential resets. ¹

How do I handle third-party remote support tools that create sessions into the environment?

Put them under the same session rules: short sessions, strong authentication, logging, and rapid revocation. Require contractual and technical controls that let you terminate sessions and review activity. ¹

Our legacy app can’t change its session mechanism quickly. What’s a reasonable compensating approach?

Put controls in front of it: SSO with strict session lifetime, a reverse proxy or gateway enforcing TLS and headers, network restrictions, and monitoring for anomalous sessions. Document the limitation, the compensating controls, and a remediation plan. ¹

Where do most programs get stuck operationalizing session authenticity?

They don’t have a single owner for session policies across the IdP and applications, so settings drift and evidence is incomplete. Assign control ownership and collect recurring evidence centrally so you can prove consistent operation. ¹

Footnotes

1. NIST SP 800-171 Rev. 3