2025 Zero-Day Storm: SharePoint and CrushFTP Under Active Attack

🛡️ The July 2025 Zero-Day Storm: SharePoint and CrushFTP Under Active Attack

The cybersecurity landscape was rocked in July 2025 by two major zero-day) exploitations that sent shockwaves through enterprise security teams worldwide. The month began with what appeared to be business as usual, but quickly escalated into a critical situation as attackers weaponized newly discovered vulnerabilities in Microsoft SharePoint and CrushFTP, leaving hundreds of organizations scrambling to patch and assess damage.

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🔧 The SharePoint "ToolShell" Crisis: A Perfect Storm

On July 18, 2025, Dutch cybersecurity firm Eye Security detected suspicious activity on a client's SharePoint server. The investigation revealed a sophisticated zero-day attack exploiting CVE-2025-53770, a critical remote code execution vulnerability with a CVSS score of 9.8.

This zero-day bypassed Microsoft's July Patch Tuesday updates, and was dubbed "ToolShell" by researchers—highlighting how incomplete fixes can be exploited by determined adversaries.

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🔍 Technical Breakdown

The exploit chain combines two vulnerabilities:

• Unsafe deserialization allows unauthenticated remote code execution.
• Attackers send specially crafted HTTP POST requests to /_layouts/15/ToolPane.aspx with a spoofed Referer: /layouts/SignOut.aspx.

Once exploited, attackers drop spinstall0.aspx, a reconnaissance tool that:

• Steals MachineKey configuration including:
  • ValidationKey
  • DecryptionKey
• Grants access to forge __VIEWSTATE payloads accepted as legitimate by SharePoint.

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🔁 Persistence Mechanism

With stolen cryptographic secrets, attackers maintain access even after patching:

“This approach makes remediation particularly difficult—a typical patch would not automatically rotate these stolen cryptographic secrets, leaving organizations vulnerable even after they patch.”
— Benjamin Harris, watchTowr

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🌍 Global Impact

• 🚨 400+ organizations breached
• ⏱️ 85+ SharePoint servers compromised within hours
• 🏢 29 major firms and government entities confirmed victims
• 🌐 9,000+ internet-exposed instances at risk

Affected sectors:

• Government
• Universities
• Energy
• Telecommunications
• Healthcare

⚠️ Notably, the National Nuclear Security Administration (NNSA) was among the victims.

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📂 CrushFTP: The Second Zero-Day Punch

Also on July 18, 2025, attackers exploited CVE-2025-54309 in CrushFTP, a managed file transfer solution. The bug, with a CVSS score of 9.0, enables remote admin access when the DMZ proxy is disabled.

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🔬 Reverse Engineering Angle

According to CrushFTP:

"Hackers apparently reverse engineered our code and found some bug which we had already fixed."

The vulnerability was inadvertently patched during unrelated AS2 bug fixes, but older versions remained exposed.

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📊 CrushFTP Impact

• 🌎 250,000+ exposed instances (Shodan)
• 🔍 1,040 unpatched servers confirmed (Shadowserver)
• 📦 Affects versions:
  • v10 < 10.8.5
  • v11 < 11.3.4_23

Attackers could:

• Create new admin users
• Modify file transfer configurations
• Maintain persistent access

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🌐 Broader July 2025 Threat Landscape

These incidents were part of a broader wave of zero-day activity:

• 🧱 Microsoft Patch Tuesday 0-days:
  • CVE-2024-38080 – Hyper-V escalation
  • CVE-2024-38112 – MSHTML spoofing
• 🔐 FortiManager exploited (CVE-2024-47575)
• ⚠️ Citrix Bleed 2 (CVE-2025-5777) triggered emergency mandates

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🕵️ Attribution & Threat Actors

• Chinese state-sponsored groups suspected in SharePoint intrusions (per Google & Microsoft)
• Three attack clusters identified (SentinelOne)
• In-memory, fileless attacks evaded detection
• Reused IP infrastructure from Ivanti exploits (Check Point)

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🛠️ Emergency Response & Patching

Microsoft:

• Released out-of-band patches (July 19–21)
• Provided AMSI & cryptographic key rotation guidance
• Published IOCs & hunting tips

CISA:

• Added CVE-2025-53770 to KEV catalog
• Issued immediate federal patch requirements
• Published joint advisories with EU partners

Industry:

• Vendors released YARA/SIGMA rules
• Cloud WAF providers deployed emergency mitigations

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📚 Key Lessons for Cybersecurity Professionals

1. Incomplete patches are dangerous
2. Assume breach for internet-facing systems
3. Cryptographic key management is essential
4. Advanced EDR and behavioral monitoring are critical

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🚨 Looking Ahead: The New Normal

The July 2025 zero-day storm marks a turning point in cybersecurity strategy.

• 116+ zero-days exploited in 2024, with more in 2025

• State-sponsored actors and aging enterprise infrastructure = perfect storm

In this new era, zero-day readiness is a survival skill, not a luxury.

📌 Organizations must:

• Shorten patch cycles
• Deploy assume-compromise strategies
• Maintain visibility and readiness

🧠 The question isn’t if you’ll face a zero-day—but when.