CVE-2026-2740

Executive Summary

CVE-2026-2740 is a critical authenticated remote code execution (RCE) vulnerability affecting multiple Zohocorp ManageEngine products: ADSelfService Plus (before build 6525), DataSecurity Plus (before build 6264), and RecoveryManager Plus (before build 6313). The flaw originates from a bug in a third-party dependency used by these products, allowing an authenticated attacker to execute arbitrary code on the target agent machine. With a CVSS score of 8.4, this vulnerability poses a severe risk to enterprise environments where these tools are deployed for identity management, data security, and backup recovery. No public proof-of-concept (PoC) or exploit code is currently available, but the risk of weaponization remains high given the criticality and the vendor's widespread adoption.

Supply Chain & Package Security

The vulnerability is rooted in a third-party dependency, highlighting a classic supply chain risk. The exact dependency is not disclosed, but the bug allows code execution through the agent component. Organizations must inventory all ManageEngine installations and ensure the dependency is patched via the vendor's update.

CVSS Breakdown & Threat Level

• CVSS Score: 8.4 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: Low (PR:L) – attacker needs valid credentials.
• User Interaction: None (UI:N) – no user action needed.
• Scope: Unchanged (S:U) – vulnerability does not cross trust boundaries.
• Confidentiality Impact: High (C:H) – full data compromise.
• Integrity Impact: High (I:H) – full system control.
• Availability Impact: High (A:H) – potential denial of service.

Threat Level: Critical. The combination of low attack complexity, network exploitability, and high impact makes this a prime target for ransomware groups and APTs.

Deep Dive & Mechanics

The vulnerability resides in the agent component of ManageEngine products. The agent communicates with the central server to receive tasks and updates. A bug in a third-party library used for parsing or processing data allows an authenticated attacker to inject malicious payloads. When the agent processes this crafted data, it leads to arbitrary code execution with the privileges of the agent process (typically SYSTEM or root).

The exact dependency is not publicly named, but based on similar past vulnerabilities in ManageEngine products, it could involve libraries for XML parsing, JSON deserialization, or template engines. The attack flow is:

1. Attacker authenticates to the ManageEngine server (e.g., via a valid user account).
2. Attacker sends a specially crafted request to the server that is forwarded to the agent.
3. The agent's vulnerable dependency processes the malicious data.
4. Code execution occurs on the agent machine.

Vulnerable vs. Patched Code

Since the vulnerability is in a third-party dependency, the fix involves updating that dependency. No code diff is publicly available. The patched versions (6525, 6264, 6313) include the updated dependency that sanitizes input or fixes the parsing flaw.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Valid credentials for the ManageEngine server.
• Network access to the server (port 443 or custom port).
• Target agent machine must be online and connected.

Exploitation Steps:

1. Identify the ManageEngine server and agent endpoints.
2. Authenticate and obtain a session token.
3. Craft a malicious payload targeting the vulnerable dependency (e.g., a serialized object or malformed XML).
4. Send the payload to the server's agent communication endpoint.
5. The agent executes the payload, granting a reverse shell or command execution.

Example Payload (Conceptual):

import requests

target = "https://manageengine-server:8443"
session = requests.Session()
# Authenticate
login_data = {"username": "attacker", "password": "password"}
session.post(f"{target}/j_security_check", data=login_data)

# Craft malicious payload (example for a deserialization bug)
payload = b"..."  # Serialized object with command
response = session.post(f"{target}/agent/execute", data=payload)
print(response.text)

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual agent-server communication patterns.
• Alert on failed authentication attempts followed by successful exploitation.
• Use the Sigma and YARA rules below.

Hardening:

• Apply the vendor patch immediately.
• Restrict agent communication to trusted networks only.
• Enable logging and audit trails on the ManageEngine server.
• Use network segmentation to isolate agent machines.

Indicators of Compromise (IOCs)

• Network:
  • Unusual outbound connections from agent machines to unknown IPs.
  • Anomalous data in agent communication channels (e.g., base64-encoded commands).
• File:
  • Temporary files created in agent directories (e.g., C:\Program Files\ManageEngine\Agent\tmp\*.exe).
  • Modified configuration files (agent.properties, server.conf).
• Process:
  • Agent process spawning cmd.exe, powershell.exe, or /bin/sh.
  • Unexpected child processes from the agent executable.
• Registry (Windows):
  • New run keys added by the agent process.

Detection Engineering

YARA Rule

rule CVE_2026_2740_ManageEngine_RCE {
    meta:
        description = "Detects malicious payloads targeting CVE-2026-2740 in ManageEngine agents"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-2740"
    strings:
        $s1 = "ManageEngine" ascii wide nocase
        $s2 = "agent" ascii wide nocase
        $s3 = "execute" ascii wide nocase
        $s4 = "Runtime" ascii wide nocase
        $s5 = "Process" ascii wide nocase
    condition:
        all of ($s*) and filesize < 10MB
}

Sigma Rule

title: CVE-2026-2740 ManageEngine Agent RCE
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects exploitation attempts of CVE-2026-2740 via agent communication
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\agent.exe'
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\wscript.exe'
            - '\cscript.exe'
    condition: selection
falsepositives:
    - Legitimate administrative tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-2740 ManageEngine Agent RCE Outbound"; flow:to_server,established; content:"|00 00 00 00|"; depth:4; content:"ManageEngine"; nocase; distance:0; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Upgrade to the patched versions:
   • ADSelfService Plus: Build 6525 or later.
   • DataSecurity Plus: Build 6264 or later.
   • RecoveryManager Plus: Build 6313 or later.
2. Workaround: If patching is not possible, restrict network access to the ManageEngine server and agent machines. Use application allowlisting to prevent unauthorized executables.
3. Monitoring: Enable detailed logging on the ManageEngine server and agent machines. Correlate logs with the Sigma rule above.
4. Incident Response: If exploitation is suspected, isolate affected machines, collect forensic data, and review agent logs for anomalies.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert