CVE-2017-12629 in Solr
Summary
by MITRE
Remote code execution occurs in Apache Solr before 7.1 with Apache Lucene before 7.1 by exploiting XXE in conjunction with use of a Config API add-listener command to reach the RunExecutableListener class. Elasticsearch, although it uses Lucene, is NOT vulnerable to this.
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Analysis
by VulDB Data Team • 01/03/2023
Apache Solr versions prior to 7.1 contain a critical remote code execution vulnerability that stems from improper handling of external entity references within the configuration API. This vulnerability specifically affects the interaction between Apache Solr's Config API and Apache Lucene's XML parsing mechanisms, creating an exploitable path through the use of XML External Entity processing. The flaw allows attackers to execute arbitrary code on the target system by leveraging the add-listener command functionality within the Config API to reach the RunExecutableListener class. This represents a sophisticated attack vector that combines XML external entity injection with command execution capabilities, making it particularly dangerous for web applications that rely on Solr for search functionality.
The technical exploitation occurs when an attacker crafts a malicious XML payload that includes external entity references pointing to malicious content or local files. When this malformed XML is processed through the Config API's add-listener command, the system attempts to load and execute the referenced entities through the RunExecutableListener class, which serves as a bridge between the XML parsing layer and the system command execution layer. This vulnerability operates at the intersection of several security domains including XML processing, configuration management, and command execution, making it particularly challenging to defend against. The attack requires the target system to be configured to accept external entity references, which is often enabled by default in certain Solr configurations, and the attacker must have access to the Config API endpoints.
The operational impact of this vulnerability extends far beyond simple data compromise, as successful exploitation can lead to complete system takeover. An attacker who gains remote code execution can access sensitive data, modify system configurations, install backdoors, and potentially use the compromised system as a pivot point to attack other systems within the network. The vulnerability affects organizations using vulnerable Solr versions in production environments where search functionality is critical, such as e-commerce platforms, content management systems, and enterprise search applications. The risk is amplified because Solr is often deployed in environments where it may have elevated privileges or access to sensitive data repositories, and the attack can be executed from remote locations without requiring authentication to the system itself.
Organizations should immediately upgrade to Apache Solr 7.1 or later versions where this vulnerability has been patched. The mitigation strategy should include implementing proper XML parsing restrictions and disabling unnecessary external entity processing in all Solr configurations. Network segmentation and access controls should be enforced to limit exposure of the Config API endpoints to trusted internal systems only. Security monitoring should be enhanced to detect unusual patterns in API usage and potential XML payload submissions. Additionally, implementing web application firewalls and input validation controls can provide additional layers of protection against such attacks. This vulnerability aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and represents a typical example of how configuration management flaws can lead to remote code execution in enterprise search systems. The ATT&CK framework categorizes this as a command and control activity involving exploitation of configuration weaknesses and privilege escalation through remote code execution. Organizations should also consider implementing automated patch management processes to ensure timely deployment of security updates across all Solr instances within their infrastructure.