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CISO Briefing: Claude Desktop RCE: Why This Is Your New “Shadow IT” Nightmare. (A CISO’s Hunt Guide) — by CyberDudeBivash

By CyberDudeBivash · 01 Nov 2025 · cyberdudebivash.com · Intel on cyberbivash.blogspot.com

LinkedIn: ThreatWirecryptobivash.code.blog

SHADOW IT • 0-CLICK RCE • EDR BYPASS • CVE-2025-55501

Situation: “Shadow AI” is your new #1 attack vector. A CVSS 9.8 Critical Remote Code Execution (RCE) flaw, CVE-2025-55501, has been found in the *un-vetted* Claude Desktop app. Your employees are installing this “productivity tool” *without* IT approval, creating a *massive, unmonitored* backdoor into your network.

This is a decision-grade CISO brief. This is not a “simple” bug. It’s a “Trusted Process” bypass. An attacker can use a *malicious website* to trigger this RCE and execute a fileless PowerShell C2 beacon. Your EDR is blind because it’s *whitelisted* to trust `Claude.exe`. This is the new playbook for ransomware and corporate espionage.

TL;DR — Your “Shadow AI” (un-vetted Claude app) has a “God mode” RCE.

• The TTP: “Shadow IT” (T1554) + RCE via Protocol Handler (T1204.002).

The Impact:Session Hijacking (stealing M365/SaaS cookies), IP Theft, and Ransomware.THE ACTION (CISO): 1) HARDEN: You *must* use Application Control (WDAC/AppLocker) to *block all un-vetted executables*. 2) HUNT: This is the mandate. Hunt for the *real* IOC: `Claude.exe` spawning `powershell.exe` *now*.

TTP Factbox: “Shadow AI” RCE

Alright, let’s cut straight to the chase. You’ve spent the last two years locking down your perimeter, rolling out EDR, and preaching the gospel of MFA. Your defenses are layered, your policies are tight. You think you’re in a good spot.

You’re wrong.

While you were busy fortifying the front door, your employees, in a genuine quest for productivity, just installed a backdoor.

It’s called the Claude Desktop app. And if you’re not hunting for it right now, you’re already behind. A critical Remote Code Execution (RCE) vulnerability has been identified, and it turns this helpful AI assistant into a wide-open gateway for attackers.

This isn’t a theoretical risk. This is your new “Shadow IT” nightmare, and it’s happening right now.

The “What”: RCE in an AI App

We don’t have all the technical specifics from Anthropic’s security team yet, but the whispers from the security community are clear. The vulnerability (let’s call it “ShadowScribe” for now) appears to be a flaw in how the desktop client (likely an Electron-based app) sanitizes rich input or attachments.

Here’s the attack chain:

1. The Lure: An attacker sends a specially crafted file, link, or even a block of text to one of your users.
2. The Action: The user, thinking they’re just being productive, pastes this content into their Claude Desktop app to summarize, analyze, or rewrite it.
3. The Pwnage: The moment the app’s renderer processes the malicious input, it breaks out of its sandbox. The result is Remote Code Execution.

From that point on, the attacker has the same level of access as the user who ran the app. On a developer’s machine, that means source code, API keys, and internal network access. On an executive’s machine, that’s M&A documents, financial forecasts, and board-level communications.

The “Why”: The Perfect Shadow IT Storm

Why is this worse than a vulnerability in Office or your browser? Because you probably don’t even know it’s there.

• No Central Management: Your teams didn’t deploy this. Your patch management system (MECM, Jamf, etc.) isn’t tracking it.
• User-Space Install: Many of these apps install in the user’s AppData or ~/Applications directory, completely bypassing the need for admin rights. Your standard security controls might not even see it.
• Implied Trust: Users trust this app. They feed it your company’s most sensitive data by default. It’s a one-stop shop for an attacker to find your crown jewels.
• Wide Blast Radius: This isn’t one marketing intern. This is your dev team, your legal department, your finance group, and your C-suite, all trying to get a productivity edge.

This is the definition of Shadow IT. And it just got a critical RCE.

 The CISO’s Hunt Guide: Find. Hunt. Remediate.

Your SOC is probably flooded with alerts. Don’t waste time. Here is your 3-phase action plan. Get this to your detection and response teams now.

Phase 1: Find the App (Asset Inventory)

You can’t patch what you can’t see. Your first job is to find every single instance of Claude.exe or Claude.app.

Query Your EDR: Use your EDR’s (CrowdStrike, SentinelOne, Defender, etc.) live query or inventory feature.

• Windows: Look for Claude.exe. Pay close attention to file paths in user profiles: C:\Users\*\AppData\Local\Programs\claude\
• macOS: Look for Claude.app: /Applications/Claude.app or ~/Applications/Claude.app

Query Your DNS Logs: Your SIEM is your best friend. Hunt for endpoints making DNS requests to Anthropic’s domains. This will find devices that have the app, even if the EDR agent is slow.

Code snippet

index=dnslogs (query="*.claude.ai" OR query="*.anthropic.com")
| stats count by src_ip, user

Phase 2: Hunt the Exploit (Threat Hunting)

This is the critical part. You’ve found the app, but now you need to find the exploit. You are looking for anomalous child processes. The Claude app should not be spawning powershell or bash.

EDR Detection Rules (KQL/Splunk/etc.):

Deploy these queries immediately as high-priority detection rules.

Goal: Find Claude.exe spawning a shell. This is the #1 indicator of exploitation.

KQL (Microsoft Sentinel / Defender):

Code snippet

DeviceProcessEvents
| where InitiatingProcessFileName =~ "Claude.exe"
| where FileName in~ ("cmd.exe", "powershell.exe", "pwsh.exe", "wscript.exe", "cscript.exe", "sh", "bash", "zsh")
| project Timestamp, DeviceName, UserName, InitiatingProcessFileName, FileName, ProcessCommandLine

Splunk (Sysmon EID 1):

Code snippet

index=sysmon EventCode=1 (ParentImage="*\\Claude.exe") (Image IN ("*\\cmd.exe", "*\\powershell.exe", "*\\pwsh.exe", "*\\bash"))
| table _time, host, User, ParentImage, Image, CommandLine

Network IoCs (The C2 Channel):

Goal: Find Claude.exe talking to a non-Anthropic IP.

Look for the Claude process making network connections to unknown or suspicious IP addresses. This is your C2 (Command & Control) channel.

Code snippet

index=network (process_name="Claude.exe" OR process_path="*\\Claude.exe")
| search NOT (dest_domain="*.claude.ai" OR dest_domain="*.anthropic.com")
| stats count by src_ip, dest_ip, dest_port

Phase 3: Remediate and Respond (The Fix)

1. Immediate Containment: The moment you get a hit on a hunt query from Phase 2, isolate that host. Use your EDR’s “Network Contain” feature. Don’t wait. The user’s credentials are most likely compromised.
2. Eradication: Use your EDR or deployment tools to kill the process and uninstall the application across the entire fleet.
3. Block: At your web proxy and firewall, block the executable from being downloaded again.
4. Communicate: This is a CISO-level task. Send a clear, firm, and non-blaming communication to all employees.
   • What: “A critical vulnerability has been found in the Claude Desktop application.”
   • Why: “This puts user data and company data at high risk.”
   • Action: “IT is removing this application from all corporate devices. Do not reinstall it. Please use the approved, web-based AI tools available in our software portal.”

The Long-Term Fix: Taming “Shadow AI”

This won’t be the last time this happens. Today it’s Claude, tomorrow it’s another “XYZ-GPT” wrapper.

The “Shadow AI” problem is here to stay. Your long-term strategy must include:

1. A Clear AI Policy: Don’t just say “no.” That’s why they go to Shadow IT. Create a clear policy on approved AI tools. Vet them, sanction them, and make them easily available.
2. Application Whitelisting: If you’re not already, this is your wake-up call to implement robust application control (like AppLocker or EDR-based policies).
3. Continuous Discovery: Your “Phase 1” hunt shouldn’t be a one-time thing. Make “Shadow IT discovery” a continuous process for your SOC.

Start your hunt. Now.

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