---
title: Potential Cisco FMC Deserialization Exploit (CVE-2026-20131)
id: 8f3a2b1c-4d5e-6f7a-8b9c-0d1e2f3a4b5c
description: Detects potential exploitation attempts against Cisco Secure Firewall Management Center via suspicious web request patterns indicative of deserialization attacks.
status: experimental
author: Security Arsenal Research
date: 2026/04/18
references:
    - https://cisa.gov/known-exploited-vulnerabilities-catalog
logsource:
    category: webserver
detection:
    selection:
        c-uri|contains:
            - '/ui/fp'
            - '/+CSCOE'
        sc-status:
            - 500
            - 200
    filter:
        c-user-agent|contains:
            - 'Mozilla'
    condition: selection and not filter
falsepositives:
    - Legitimate administrative access
tags:
    - attack.initial_access
    - cve.2026.20131
    - ransomware.coinbasecartel
level: high

---
title: SmarterTools SmarterMail Authentication Bypass (CVE-2026-23760)
id: 9a4b3c2d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
description: Identifies authentication bypass attempts on SmarterMail servers using alternate path channels.
status: experimental
author: Security Arsenal Research
date: 2026/04/18
references:
    - https://cisa.gov/known-exploited-vulnerabilities-catalog
logsource:
    category: webserver
detection:
    selection:
        c-uri|contains:
            - '/Services/Mail.asmx'
            - '/LiveChat/'
        cs-method: 'POST'
    condition: selection
falsepositives:
    - Legitimate API usage
level: medium
tags:
    - attack.initial_access
    - cve.2026.23760
    - ransomware.coinbasecartel

---
title: Ransomware Pre-Encryption Shadow Copy Deletion
id: 1b2c3d4e-5f6a-7b8c-9d0e-1f2a3b4c5d6e
description: Detects commands used to delete Volume Shadow Copies via vssadmin or PowerShell, a common precursor to encryption by COINBASECARTEL affiliates.
status: experimental
author: Security Arsenal Research
date: 2026/04/18
logsource:
    category: process_creation
    product: windows
detection:
    selection_vssadmin:
        Image|endswith: '\vssadmin.exe'
        CommandLine|contains: 'delete shadows'
    selection_powershell:
        Image|endswith: '\powershell.exe'
        CommandLine|contains: 
            - 'Get-WmiObject Win32_ShadowCopy'
            - 'Remove-WmiObject'
    condition: 1 of selection*
falsepositives:
    - System administration tasks
level: critical
tags:
    - attack.impact
    - ransomware.coinbasecartel

// Hunt for lateral movement and credential dumping indicative of COINBASECARTEL prep
let ProcessCreationEvents = DeviceProcessEvents 
| where Timestamp >= ago(7d);
ProcessCreationEvents 
| where FileName in~ ('cmd.exe', 'powershell.exe', 'pwsh.exe', 'powershell_ise.exe') 
| where ProcessCommandLine has any('wmic', 'tasklist', 'whoami', 'net user', 'quser') 
or ProcessCommandLine has_any('/share', '\\', 'downloadstring', 'iex')
| summarize Count = count(), StartTime = min(Timestamp), EndTime = max(Timestamp) by DeviceName, AccountName, FileName, ProcessCommandLine 
| where Count > 5 
| order by Count desc

<#
    COINBASECARTEL Response Script: Check for RDP Brute Force Indicators and Scheduled Task Persistence
    Run as Administrator on suspected endpoints.
#>

Write-Host "[*] Checking for recent suspicious Scheduled Tasks (Last 7 Days)..." -ForegroundColor Cyan
$dateCutoff = (Get-Date).AddDays(-7)
$suspiciousTasks = Get-ScheduledTask | Where-Object { $_.Date -gt $dateCutoff }

if ($suspiciousTasks) {
    Write-Host "[!] WARNING: Found recently created/modified scheduled tasks:" -ForegroundColor Red
    $suspiciousTasks | Select-Object TaskName, Date, Author | Format-Table -AutoSize
} else {
    Write-Host "[+] No suspicious recent task creation found." -ForegroundColor Green
}

Write-Host "[*] Analyzing Security Event Log for RDP Logon Failures (Possible Brute Force)..." -ForegroundColor Cyan
$rdpFailures = Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4625; StartTime=$dateCutoff} -ErrorAction SilentlyContinue

if ($rdpFailures) {
    $failCount = ($rdpFailures | Measure-Object).Count
    Write-Host "[!] WARNING: $failCount failed logon attempts detected in the last 7 days." -ForegroundColor Red
    $targetUsers = $rdpFailures | Select-Object -First 20 @{N='Username';E={$_.Properties[5].Value}}, @{N='IP';E={$_.Properties[19].Value}}
    $targetUsers | Format-Table -AutoSize
} else {
    Write-Host "[+] No excessive RDP failures detected." -ForegroundColor Green
}

Write-Host "[*] Checking for Volume Shadow Copy Manipulation..." -ForegroundColor Cyan
$vssCheck = Get-WinEvent -FilterHashtable @{LogName='Application'; ProviderName='VSS'; StartTime=$dateCutoff} -ErrorAction SilentlyContinue | Where-Object {$_.Message -like '*error*' -or $_.Message -like '*delete*'}
if ($vssCheck) {
    Write-Host "[!] WARNING: VSS Errors or Deletions detected." -ForegroundColor Red
} else {
    Write-Host "[+] VSS health nominal." -ForegroundColor Green
}


---

# Incident Response Priorities

**T-Minus Detection Checklist:**
1.  **Edge Device Logs:** Immediately review logs for Cisco FMC, Citrix ADC, and Fortinet devices for anomalies corresponding to CVE-2026-20131, CVE-2025-5777, and CVE-2019-6693.
2.  **Mail Server Logs:** Audit SmarterMail (CVE-2026-23760) logs for authentication bypass attempts or unusual administrative logins.
3.  **Web Shells:** Scan web roots for recently modified files (last 48h) containing base64 encoded payloads or `eval()` functions consistent with React RCE exploitation.

**Critical Assets for Exfiltration:**
Based on the victimology (Education, Media, Govt), prioritize the search for exfiltrated data in:
*   Student/Personnel PII databases.
*   Intellectual property (Engineering blueprints).
*   Financial systems and donor lists.

**Containment Actions (Urgency: High):**
1.  **Isolate:** Disconnect internet-facing VPNs and Firewalls from the internal network immediately if compromise is suspected.
2.  **Reset:** Force-reset all privileged credentials (Domain Admin, Local Admin) used on perimeter devices.
3.  **Block:** Block inbound IP ranges associated with recent anomalous traffic at the edge firewall.

---

# Hardening Recommendations

**Immediate (24 Hours):**
*   **Patch Critical KEVs:** Apply patches for CVE-2026-20131 (Cisco FMC), CVE-2026-23760 (SmarterMail), and CVE-2025-5777 (Citrix). These are confirmed active exploitation vectors.
*   **Disable MFA Bypass:** Ensure MFA is strictly enforced on all VPN and management interfaces; disable local account fallback where possible.
*   **Network Segmentation:** Ensure management interfaces for firewalls (SSH/HTTPS) are NOT accessible from the public internet. Require VPN connectivity to reach them.

**Short-Term (2 Weeks):**
*   **Zero Trust Architecture:** Implement strict validation for all internal lateral movement, specifically PsExec and WMI execution.
*   **Web Application Firewalls (WAF):** Update WAF rules to block known signatures for the React Server Components RCE and SmarterMail authentication bypass.
*   **Credential Hygiene:** Audit and rotate any credentials found in hardcoded configurations (specifically Fortinet VPN credentials).

---