Microsoft Scrambles to Patch SharePoint Flaw After Cyberattacks Exploit Zero-Day Vulnerability

On-premise servers hit in stealthy attacks, prompting urgent security advisory for IT admins worldwide

Microsoft has rushed out an emergency patch after cyberattackers exploited a newly discovered vulnerability in SharePoint Server. The flaw, already used in real-world attacks, triggered alarm bells across enterprise IT departments, especially those relying on on-premise systems.

The company confirmed the issue affects SharePoint Server 2016 and 2019 and is being actively weaponized. The urgency of the patch underscores the growing threat posed by increasingly sophisticated state-sponsored and criminal hacking groups.

Not Just a Bug — It Was Already Being Used

Microsoft didn’t just stumble upon this vulnerability. The company says it was informed by an external source that attackers were already exploiting it. That instantly pushed it into the “zero-day” category — a term used for security holes found by hackers before the vendor knows about it.

In short, some attackers knew about it before Microsoft did.

The vulnerability is tracked as CVE-2024-38021, and it allows attackers to trick SharePoint into running malicious scripts or commands. The attack vector? A specially crafted API request — something easily missed in logs unless you’re looking for it.

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Microsoft says this exploit can bypass authentication if the attacker already has access to the internal network. That makes it especially dangerous for companies running SharePoint behind a firewall, assuming they’re safe from outside threats.

Who’s Most at Risk? Old Systems, Weak Defenses

Not every SharePoint customer is equally exposed. Microsoft 365 users — those on the cloud — are in the clear. This only affects organizations running SharePoint on their own hardware, usually for performance, compliance, or privacy reasons.

But those reasons are now liabilities.

Cybersecurity analysts warn that self-hosted systems often lag behind in updates, especially in bureaucratic or resource-constrained organizations. That’s a big problem when dealing with zero-days.

Some companies still run SharePoint 2016 in production. Others haven’t patched in months.

Here’s who’s most vulnerable right now:

• Organizations running SharePoint Server 2016 or 2019

• Enterprises with on-premise infrastructure not behind a strict patching schedule

• Systems exposed to internal lateral movement after an initial breach

Attackers are increasingly chaining vulnerabilities together. That means once they’re inside a network via phishing or VPN flaws, SharePoint becomes a juicy second target.

The Fix: Get the Patch Now, or Risk a Breach

Microsoft released the patch as part of its July 2025 Patch Tuesday rollout, but this one comes with big red warning signs. The company strongly urges IT teams to apply the update immediately, even if that means a temporary service disruption.

But the patch alone isn’t enough. According to Microsoft, systems must also have “SharePoint Server Subscription Edition Version 23H2” or the July security update installed for the fix to take full effect.

Some admins found the patch didn’t install properly at first. Microsoft later clarified that additional configuration steps might be needed, including manual service restarts and running PowerShell commands.

It’s a messy fix, but not as messy as a breach.

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Even more confusing: some reports suggested Microsoft’s documentation initially lacked clarity, with admins turning to forums and Reddit for help deciphering the instructions. That has since been updated.

Bigger Pattern Emerging: Microsoft Enterprise Tools Under Fire

This isn’t the first time Microsoft’s enterprise platforms have been targeted this year. Exchange, Outlook, Teams — all have faced critical vulnerabilities since January, many of which were exploited before patches were available.

A recent report by Mandiant noted that state-sponsored attackers from Asia and Eastern Europe are increasingly prioritizing Microsoft infrastructure due to its widespread use in government and corporate environments.

Here’s a quick snapshot of Microsoft enterprise vulnerabilities exploited this year:

Many security experts argue Microsoft’s focus on cloud services has left legacy on-premise tools more vulnerable. “These systems don’t get the same engineering love anymore,” said one former Microsoft engineer on X.

What IT Teams Are Doing Right Now

Across Fortune 500 companies and mid-sized businesses alike, IT admins are scrambling to review logs, patch servers, and update firewalls. For many, this vulnerability hit close to home — literally. SharePoint powers internal wikis, HR tools, and document workflows.

One admin at a mid-sized bank in Chennai said they had to work through the night.

“We got the advisory at 4 a.m. and were patching by 6. This isn’t something you sleep on.”

Another sysadmin, posting anonymously, admitted their servers hadn’t been patched since April. “Our IT director wants full regression testing before updates. Guess we’ll see how that works when we’re breached.”

Such delays are common. Security often takes a backseat to uptime — until a breach forces everyone to reconsider.

Cloud vs On-Prem Debate Reignites

The incident has reignited a familiar debate in enterprise tech circles: Is it still worth running on-prem infrastructure?

For many, the answer remains yes. Regulatory compliance, latency needs, and control over data often justify it. But each new zero-day makes the argument harder to defend.

Security experts point out that Microsoft 365 customers didn’t have to lift a finger during this crisis. No patches. No late-night teams. Just business as usual.

On-prem teams, meanwhile, faced:

• Confusing install instructions

• Fear of ongoing exploits

• Constant log monitoring for signs of compromise

As cyberattacks evolve, the cost of control may start to outweigh the benefits. And more organizations could shift to the cloud — not for convenience, but for survival.