CVE-2018-1285 in Enterprise Manager Base Platform
Summary
by MITRE
Apache log4net versions before 2.0.10 do not disable XML external entities when parsing log4net configuration files. This allows for XXE-based attacks in applications that accept attacker-controlled log4net configuration files.
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Analysis
by VulDB Data Team • 11/13/2022
The vulnerability identified as CVE-2018-1285 affects Apache log4net versions prior to 2.0.10 and represents a critical security flaw that enables XML External Entity (XXE) attacks through improper configuration file parsing. This vulnerability specifically targets applications that utilize log4net for logging purposes and accept user-controlled configuration files, creating a pathway for remote attackers to exploit the system through maliciously crafted configuration inputs. The flaw stems from the library's failure to properly disable XML external entity processing during the parsing of configuration files, which is a fundamental security measure that should be enabled by default to prevent unauthorized access to system resources.
The technical implementation of this vulnerability occurs when an application using log4net processes configuration files that contain malicious XML content with external entity declarations. When the library parses these configuration files without disabling external entity resolution, it allows attackers to reference external resources that can be used to perform various malicious activities including data exfiltration, server-side request forgery, or denial of service attacks. The vulnerability is particularly dangerous because it operates at the configuration parsing level, meaning that even applications that properly secure their logging mechanisms can be compromised through a malicious configuration file. This flaw aligns with CWE-611, which specifically addresses improper restriction of XML external entity reference, and represents a classic example of how XML processing can be exploited when security controls are not properly implemented.
The operational impact of CVE-2018-1285 extends beyond simple data exposure, as it can enable attackers to perform reconnaissance on internal systems, access sensitive files, or even establish command and control channels through the log4net configuration parsing mechanism. Applications that allow user input to influence logging configuration are particularly vulnerable, as attackers can inject malicious XML content that will be processed by the vulnerable log4net library. This vulnerability can be exploited in scenarios where configuration files are loaded from untrusted sources, such as web applications that allow user-uploaded configuration files, or systems where configuration data is fetched from external sources without proper validation. The attack vector typically involves crafting a malicious configuration file that contains XML external entity declarations pointing to attacker-controlled resources, which then gets processed by the vulnerable log4net library.
Mitigation strategies for CVE-2018-1285 primarily focus on upgrading to Apache log4net version 2.0.10 or later, which includes proper XML external entity handling and disables external entity resolution by default. Organizations should also implement strict input validation for all configuration files, particularly those that originate from untrusted sources, and consider implementing additional security controls such as XML schema validation to prevent malicious content from being processed. The remediation process should include comprehensive testing to ensure that configuration files are properly sanitized and that the application does not inadvertently load malicious configuration data. Security teams should also monitor for any applications that may be using older versions of log4net and ensure that all dependencies are updated to versions that address this vulnerability. This vulnerability demonstrates the importance of proper XML processing security controls and aligns with ATT&CK technique T1213, which covers data from information repositories, particularly in the context of configuration file manipulation and XML external entity processing.