CVE-2020-13925: Apache Kylin RCE Vulnerability

CVE-2020-13925 Overview

CVE-2020-13925 is a critical OS command injection vulnerability affecting Apache Kylin, an open-source distributed analytics engine designed for big data workloads. Similar to CVE-2020-1956, this vulnerability exists in a RESTful API endpoint that concatenates user-supplied input directly into OS commands before executing them on the server. The affected API lacks necessary input validation, enabling remote attackers to execute arbitrary operating system commands with the privileges of the Kylin service account.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary OS commands on affected Apache Kylin servers, potentially leading to complete system compromise, data exfiltration, and lateral movement within enterprise environments.

Affected Products

• Apache Kylin versions after 2.3 and prior to 3.1.0
• Apache Kylin deployments exposed to network access
• Enterprise big data analytics environments running vulnerable Kylin instances

Discovery Timeline

• July 14, 2020 - CVE-2020-13925 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-13925

Vulnerability Analysis

This command injection vulnerability (CWE-78) stems from improper input validation in one of Apache Kylin's RESTful API endpoints. The vulnerable API accepts user-controlled input and concatenates it directly into OS command strings that are subsequently executed on the underlying server. Without proper sanitization or escaping of special characters, attackers can inject malicious command sequences that break out of the intended command context and execute arbitrary system commands.

The vulnerability is particularly dangerous because it requires no authentication and can be exploited remotely over the network. An attacker needs only network access to the Kylin API endpoint to achieve full command execution on the target system. This is the second command injection vulnerability discovered in Kylin's API layer, following CVE-2020-1956, indicating a pattern of insufficient input validation in the application's API handling code.

Root Cause

The root cause of CVE-2020-13925 is the direct concatenation of untrusted user input into OS command strings without proper validation, sanitization, or parameterization. The vulnerable RESTful API endpoint passes user-supplied data directly to shell command execution functions, allowing shell metacharacters and command separators to alter the intended command execution flow.

Attack Vector

The attack leverages the network-accessible RESTful API in Apache Kylin. An attacker crafts a malicious HTTP request to the vulnerable API endpoint, embedding OS command sequences within the API parameters. The Kylin server then processes this request, concatenating the malicious input into a command string and executing it via the system shell.

Common injection techniques that may be used include:

• Command separators such as semicolons (;), pipes (|), or ampersands (&)
• Command substitution using backticks or $() syntax
• Newline characters to break command boundaries

The exploitation of this vulnerability can result in complete server compromise, including unauthorized access to sensitive analytics data, installation of backdoors, or use of the compromised system as a pivot point for further attacks within the network.

Detection Methods for CVE-2020-13925

Indicators of Compromise

• Unusual HTTP requests to Apache Kylin API endpoints containing shell metacharacters (;, |, &, backticks, $())
• Unexpected child processes spawned by the Kylin Java process
• Anomalous outbound network connections from Kylin server instances
• Suspicious command executions logged in system audit logs originating from the Kylin service account

Detection Strategies

• Deploy web application firewalls (WAF) with rules to detect command injection patterns in API requests
• Implement network intrusion detection signatures targeting OS command injection payloads
• Monitor Apache Kylin access logs for requests containing URL-encoded shell metacharacters
• Enable process execution monitoring on Kylin servers to detect unexpected command execution

Monitoring Recommendations

• Configure centralized logging for all Apache Kylin API access and correlate with system-level audit logs
• Implement behavioral analysis to detect anomalous process creation patterns on Kylin hosts
• Monitor for data exfiltration attempts from systems hosting Apache Kylin
• Establish baseline network behavior for Kylin deployments and alert on deviations

How to Mitigate CVE-2020-13925

Immediate Actions Required

• Upgrade Apache Kylin to version 3.1.0 or later immediately
• Restrict network access to Apache Kylin API endpoints using firewall rules or network segmentation
• Implement WAF rules to block requests containing potential command injection patterns
• Review system logs for evidence of past exploitation attempts

Patch Information

Apache has addressed this vulnerability in Apache Kylin version 3.1.0. Organizations running any version after 2.3 and prior to 3.1.0 should upgrade immediately. Refer to the Apache Kylin User Mailing List for official patch details and the Apache Kylin Commit Discussion for technical commit information.

Workarounds

• Restrict access to the Apache Kylin web interface and API to trusted networks only using firewall ACLs
• Place Apache Kylin behind a reverse proxy with input validation and request filtering capabilities
• Disable or block access to non-essential API endpoints until patching is completed
• Implement application-layer authentication requirements for all API endpoints as an additional control layer

# Example: Restrict Apache Kylin access to trusted IP ranges using iptables
# Adjust the IP range and port as appropriate for your environment
iptables -A INPUT -p tcp --dport 7070 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 7070 -j DROP