Are Hybrid Environments Really Less Secure, or Just More Complex?

Introduction

Hybrid environments, those blends of on-premises infrastructure and cloud services, have become the norm for many organizations. But increasingly, they’re showing up in incident response reports, threat actor playbooks, and CVE disclosures.

So what’s the deal here? Are hybrid environments inherently less secure? Or isthere simply more complexity and more room for human error?

Let’s cut through the speculation and look at what the data, vulnerabilities, and architecture tell us.

‍Spoiler: It's not Microsoft’s fault, but it is a lot to manage. And that’s where engineers like ours here at AE Business Solutions come in.

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What Exactly Is a Hybrid Environment?

A hybrid environment typically combines:
- On-prem Active Directory (AD DS)
- Azure AD through sync (Azure AD Connect, Pass-Through Authentication, or ADFS)
- On-prem Exchange Server with Microsoft 365
- Legacy apps or services that rely on local authentication or infrastructure

Plenty of enterprises are in this middle ground. Some by design, some because migrations are in progress, and some because legacy dependencies won’t budge.

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Complexity: The Root of the Issue

Hybrid setups aren't just about infrastructure, they're about identity, integration, and inheritance.

You have:
- Multiple identity surfaces: On-prem AD and Entra ID, often with sync errorsor mismatches
- Dual logging domains: Security events split across cloud-native tools (like Sentinel or Defender) and on-prem logs
- Patch gaps: Cloud services patch automatically; on-prem software depends on scheduled maintenance and internal SLAs
- Legacy protocols and features hanging around: NTLM, IMAP, POP3, Exchange Autodiscover which are old protocols and all ripe for abuse

With every added layer comes another place to misconfigure, delay patching, or overlook a signal. That’s not theoretical, real-world exploits have proven it.

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Real Vulnerabilities That Hit Hybrid Hard

Let’s look at some CVEs and incidents that specifically impacted hybrid environments:

CVE-2021-26855 – ProxyLogon (Exchange Server RCE):
Exploited vulnerable on-prem Exchange servers. Many orgs running Exchange in hybrid mode delayed patching because they thought mail flow was “mostly cloud based.” Resulted in full system compromise across thousands of networks.

CVE-2022-26923 – Certificate Spoofing via AD CS:
Exploited in hybrid domains where certificate services were enabled. Allowed attackers to impersonate domain controllers and escalate privileges. Most impact seen in orgs with AD CS still active to support legacy on-prem services.

CVE-2023-23397 – Outlook Elevation of Privilege:
A simple calendar invite triggered NTLM authentication leaks. Hybrid environments running Outlook clients connected to both on-prem and cloud Exchange were particularly exposed.

AD FS Token Forgery (SolarWinds-style Attack):
Not CVE-tracked, but a key part of the post-exploitation phase in the SolarWinds campaign. Stolen or forged token-signing certificates in AD FS environments allowed attackers to impersonate users even with MFA in place.

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Is Microsoft Neglecting Hybrid? Not Exactly.

Let’s be clear, Microsoft isn’t abandoning hybrid. But they’ve made it clear where they’re headed: the cloud.

- Features like Conditional Access, Defender for Identity, and Privileged Identity Management are designed for Entra ID first.
- Security updates and innovations land in the cloud long before (if ever) they reach on-prem equivalents.
- Documentation assumes eventual cloud transition, not indefinite hybrid maintenance.

This doesn’t mean on-prem is unsupported. But it does mean you are responsible for filling in the gaps and keeping both sides of the house patched, logged, and locked down.

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So… Is Hybrid Less Secure?

Not inherently. But it is:
- Harder to monitor
- Easier to misconfigure
- Slower to patch
- More dependent on legacy services
- Less covered by modern tooling

In other words: It’s not less secure by design but it is less forgiving when you miss something.

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How AE Business Solutions Can Help

At AE, our security engineers have worked in the trenches of hybrid identity, on-prem Exchange hardening, and modern cloud access controls. We help organizations:

✅ Identify where hybrid components expose unnecessary risk
✅ Harden Azure AD Connect, AD FS, and legacy Exchange
✅ Align logging and alerting across on-prem and cloud platforms
✅ Plan and execute secure, staged migrations when the time is right
✅ Build security into hybrid environments, not just bolt it on later

Whether you’re committed to hybrid for the long haul or planning a full cloud move, we meet you where you are and help secure both ends.

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Conclusion

Hybrid environments aren’t the villain. But they are complicated and complexity breeds risk.

If you're going to stay hybrid, you need to secure it like it’s your primaryenvironment. Because to an attacker, it is.

Let’s get that complexity under control before someone else does.

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Author: Robert Chuvala