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🧠 Overview

CVE-2026-73570 is a high-severity OS command injection vulnerability affecting specific configurations of Zimbra Collaboration Suite.

The vulnerability involves the SNMP notification-processing component. Under vulnerable configurations, attacker-controlled data originating from SMTP processing can reach an operating-system command execution context without sufficient input neutralization.

Successful exploitation can result in remote code execution with the privileges of the Zimbra operating-system account.

🔴 Attack Vector: Network 🔓 Authentication: None 👤 User Interaction: None 💻 Impact: Remote Code Execution 📡 Attack Surface: SMTP / SNMP notification processing

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📊 Vulnerability Details

Property	Details
🆔 CVE	CVE-2026-73570
🏢 Product	Zimbra Collaboration Suite
🔥 Severity	High
📈 CVSS v3.1	8.9
🧩 CWE	CWE-78 — OS Command Injection
🌐 Attack Vector	Network
🔐 Privileges Required	None
👤 User Interaction	None
📦 Affected Release	ZCS versions before 10.1.20 under affected configuration
✅ Fixed Release	10.1.20
🚨 KEV Status	Listed in CISA KEV

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

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🔥 Attack Chain

🌐 External Attacker → 📧 SMTP Processing → ⚙️ Zimbra Components → 📡 SNMP Notification Processing → ⚠️ Insufficient Input Validation → 💻 OS Command Injection → 🚨 Remote Code Execution

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📸 Demo

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Simplified Flow

SMTP
  ↓
Zimbra
  ↓
SNMP Notification Processing
  ↓
Untrusted Input
  ↓
OS Command Injection
  ↓
Remote Code Execution

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⚙️ Affected Configuration

The vulnerable attack path is associated with installations where the relevant SNMP functionality is present and active.

ZCS < 10.1.20
       │
       ├── zimbra-snmp installed
       │
       ├── SNMP notifications enabled
       │
       └── Notification processing active

Organizations should verify their Zimbra configuration rather than assuming that every installation is vulnerable.

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🔬 Technical Root Cause

The vulnerability is categorized as:

CWE-78 — Improper Neutralization of Special Elements used in an OS Command

The security boundary can be represented as:

Untrusted Network Data
        │
        ▼
SMTP / Zimbra Processing
        │
        ▼
SNMP Notification Path
        │
        ▼
Command Construction
        │
        ▼
Shell / OS Execution

The fundamental security issue is the failure to adequately neutralize attacker-controlled input before it reaches an operating-system command execution context.

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💥 Potential Impact

Successful exploitation may allow an attacker to execute commands with the privileges available to the affected Zimbra service account.

Potential consequences include:

• 💻 Remote command execution
• 📂 Unauthorized file access
• 🔑 Exposure of credentials or sensitive information
• 🕸️ Deployment of malicious files or web shells
• 🔄 Establishment of persistence
• 🛰️ Network reconnaissance
• ↔️ Further compromise of connected systems
• 📡 Unauthorized outbound network activity

The ultimate impact depends on the privileges of the affected service account and the configuration of the surrounding environment.

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🛡️ Remediation

✅ Upgrade Zimbra

The primary remediation is to upgrade affected installations to:

Zimbra Collaboration Suite 10.1.20

or a later supported release.

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⚙️ Review SNMP Configuration

Administrators should determine whether the affected SNMP functionality is required.

Where operationally appropriate:

• Review zimbra-snmp installation
• Review SNMP notification configuration
• Disable unnecessary SNMP notifications
• Remove unnecessary components
• Apply vendor security guidance

Temporary configuration changes should not replace upgrading to a fixed release.

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🔎 Detection & Threat Hunting

Security teams should review systems for unusual activity involving:

📧 SMTP

• Unexpected SMTP sources
• Abnormally formatted recipient addresses
• Suspicious command-like input
• Unusual SMTP request patterns

📡 SNMP / Notification Processing

• Unexpected notification activity
• Abnormal process execution
• Unexpected child processes
• Suspicious command execution

💻 Host Activity

• Unexpected shells
• New or modified web-accessible files
• Suspicious persistence mechanisms
• Unexpected outbound connections
• Abnormal processes running as the zimbra user

🌐 Network Monitoring

Monitor for unusual outbound connections originating from Zimbra servers, particularly connections that do not correspond to normal mail-server operations.

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🚨 Exploitation Status

CVE-2026-73570 has been added to the CISA Known Exploited Vulnerabilities (KEV) Catalog.

Security organizations have also reported exploitation activity involving vulnerable Zimbra installations.

For internet-facing Zimbra infrastructure, administrators should prioritize:

1. Identify vulnerable installations
2. Verify SNMP configuration
3. Upgrade to a fixed release
4. Review historical logs
5. Hunt for indicators of compromise
6. Investigate unexpected processes and network connections

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🧭 Security Architecture