CVE-2022-33980: Apache Commons Configuration RCE Flaw

CVE-2022-33980 Overview

Apache Commons Configuration performs variable interpolation, allowing properties to be dynamically evaluated and expanded. The standard format for interpolation is ${prefix:name}, where "prefix" is used to locate an instance of org.apache.commons.configuration2.interpol.Lookup that performs the interpolation. Starting with version 2.4 and continuing through 2.7, the set of default Lookup instances included interpolators that could result in arbitrary code execution or contact with remote servers.

The problematic lookups are:

• script - execute expressions using the JVM script execution engine (javax.script)
• dns - resolve DNS records
• url - load values from URLs, including from remote servers

Applications using the interpolation defaults in the affected versions may be vulnerable to remote code execution or unintentional contact with remote servers if untrusted configuration values are used.

Critical Impact

This vulnerability allows attackers to achieve remote code execution through malicious variable interpolation in configuration values, potentially leading to complete system compromise.

Affected Products

• Apache Commons Configuration (versions 2.4 through 2.7)
• NetApp SnapCenter
• Debian Linux 11.0

Discovery Timeline

• 2022-07-06 - CVE-2022-33980 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-33980

Vulnerability Analysis

This vulnerability is a Code Injection flaw that exploits the variable interpolation feature in Apache Commons Configuration. The library's design allows configuration values to contain dynamic expressions that are evaluated at runtime using the ${prefix:name} syntax. The critical issue is that certain default Lookup implementations enable dangerous operations including script execution, DNS lookups, and URL fetching.

When an application processes untrusted configuration input, an attacker can craft malicious interpolation strings that leverage these lookups to execute arbitrary code on the server. The script lookup is particularly dangerous as it provides direct access to the JVM script execution engine via javax.script, enabling execution of arbitrary Java or JavaScript code within the application's security context.

Root Cause

The root cause is the inclusion of dangerous Lookup implementations in the default set of interpolators. The script, dns, and url lookups provide powerful capabilities that were enabled by default without considering the security implications when processing untrusted input. This design flaw follows a similar pattern to the widely publicized Log4Shell vulnerability (CVE-2021-44228), where JNDI lookup functionality enabled similar attack vectors.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker who can influence configuration values processed by a vulnerable application can inject malicious interpolation expressions. For example, injecting a value like ${script:javascript:java.lang.Runtime.getRuntime().exec('malicious_command')} could trigger command execution when the configuration is processed.

The vulnerability can manifest in several scenarios:

• Configuration files that accept user-controlled values
• API endpoints that process configuration parameters
• Database-stored configurations with user-modifiable fields

The attack could result in remote code execution via the script lookup, exfiltration of sensitive data via the dns lookup (DNS exfiltration), or server-side request forgery via the url lookup.

Detection Methods for CVE-2022-33980

Indicators of Compromise

• Unusual outbound DNS queries containing encoded data or unexpected subdomains
• Log entries containing ${script:, ${dns:, or ${url: patterns in configuration-related contexts
• Unexpected outbound HTTP/HTTPS connections from application servers to unknown destinations
• Java process spawning child processes or executing shell commands unexpectedly

Detection Strategies

• Implement application-level logging to capture configuration value processing and flag suspicious interpolation patterns
• Deploy network monitoring to detect anomalous DNS queries or outbound connections from application servers
• Use Web Application Firewalls (WAF) to filter input containing known malicious interpolation patterns like ${script:, ${dns:, and ${url:
• Conduct dependency scanning to identify applications using vulnerable versions of Apache Commons Configuration (2.4-2.7)

Monitoring Recommendations

• Monitor Java application logs for exceptions related to script execution or interpolation failures
• Set up alerts for unusual network traffic patterns from Java application servers
• Implement file integrity monitoring on configuration files to detect unauthorized modifications
• Establish baseline metrics for DNS query volume and alert on significant deviations

How to Mitigate CVE-2022-33980

Immediate Actions Required

• Upgrade Apache Commons Configuration to version 2.8.0 or later, which disables the problematic interpolators by default
• Audit all applications in your environment for usage of vulnerable Apache Commons Configuration versions
• Review configuration input sources to identify where untrusted data may be processed
• Implement input validation to reject configuration values containing interpolation patterns if untrusted input is unavoidable

Patch Information

Users are recommended to upgrade to Apache Commons Configuration 2.8.0, which disables the problematic interpolators (script, dns, url) by default. The fix addresses the vulnerability by removing these dangerous lookups from the default interpolator set while still allowing explicit opt-in for applications that require them.

For detailed patch information, refer to the Apache Security Mailing List Discussion. Additional advisories are available from NetApp Security Advisory NTAP-20221028-0015 and Debian Security Advisory DSA-5290.

Workarounds

• If immediate upgrade is not possible, explicitly configure the ConfigurationInterpolator to exclude the dangerous lookups (script, dns, url)
• Implement strict input validation on all configuration sources to reject values containing the ${ pattern
• Deploy network-level controls to restrict outbound connections from application servers
• Consider running Java applications with a SecurityManager policy that restricts script execution and network access

# Example: Update Maven dependency to patched version
# In pom.xml, update the dependency:
# <dependency>
#     <groupId>org.apache.commons</groupId>
#     <artifactId>commons-configuration2</artifactId>
#     <version>2.8.0</version>
# </dependency>

# Verify current version in your project
mvn dependency:tree | grep commons-configuration

# Force update to patched version
mvn versions:use-latest-versions -Dincludes=org.apache.commons:commons-configuration2