CVE-2020-25245 in DIGSI 4
Summary
by MITRE • 02/10/2021
A vulnerability has been identified in DIGSI 4 (All versions < V4.94 SP1 HF 1). Several folders in the %PATH% are writeable by normal users. As these folders are included in the search for dlls, an attacker could place dlls there with code executed by SYSTEM.
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Analysis
by VulDB Data Team • 02/26/2021
This vulnerability exists within DIGSI 4 software version 4.94 SP1 HF 1 and earlier, representing a critical privilege escalation flaw that allows unprivileged users to execute arbitrary code with SYSTEM privileges. The vulnerability stems from improper directory permissions where multiple folders within the system PATH environment variable are writable by standard users. This configuration creates a dangerous attack surface because the Windows dynamic link library (DLL) loading mechanism searches for required libraries in the PATH directories in order of their appearance. When a user executes a legitimate application that loads a DLL, the system will first search for that DLL in the directories listed in the PATH environment variable, beginning with the first directory. If an attacker can write to any of these directories, they can place a malicious DLL with the same name as a legitimate DLL that the application expects to load, causing the system to execute the attacker-controlled code with the privileges of the process that loads it.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-427 and CWE-471, which address uncontrolled search path and improper handling of environment variables. Attackers can leverage this weakness by identifying applications within the system that are running with elevated privileges and are susceptible to DLL injection through the PATH manipulation. The vulnerability is particularly concerning because it operates at the operating system level rather than within the application itself, making it difficult to detect through traditional application-level security measures. The attack vector involves placing malicious DLL files in one of the writable PATH directories, which then gets loaded by a legitimate process running as SYSTEM, effectively allowing the attacker to execute code with the highest available privileges. This type of vulnerability is categorized under the ATT&CK framework as privilege escalation through DLL side-loading, specifically targeting the T1055.001 technique for execution through DLL side-loading and T1068 for local privilege escalation.
The operational impact of this vulnerability is severe and far-reaching, as it provides attackers with a persistent backdoor mechanism that can be used to maintain access to systems without requiring additional exploitation steps. Once an attacker successfully places a malicious DLL in a PATH directory, they can execute code with SYSTEM privileges, potentially allowing them to access sensitive data, modify system configurations, install additional malware, or establish persistence mechanisms. The vulnerability affects all versions of DIGSI 4 prior to SP1 HF 1, indicating that a significant number of installations may be at risk, particularly in industrial environments where such software is commonly deployed. Organizations using DIGSI 4 in production environments face a critical security risk that could lead to complete system compromise, data breaches, and potential operational disruptions. The vulnerability's exploitation does not require specialized knowledge or complex attack chains, making it particularly dangerous as it can be leveraged by attackers with minimal technical expertise. Additionally, the fact that the vulnerability is present in the PATH environment variable means that it can affect multiple applications simultaneously, amplifying the potential impact across the entire system.
The recommended mitigation strategies include immediate application of the vendor-provided patch for DIGSI 4 version 4.94 SP1 HF 1 or later, which addresses the PATH directory permissions issue by ensuring that only authorized users have write access to directories within the system PATH. Organizations should also implement the principle of least privilege by reviewing and restricting write permissions on all directories listed in the PATH environment variable to prevent unauthorized modifications. Security administrators should conduct comprehensive audits of system PATH configurations to identify and remediate any additional directories that may be writable by non-privileged users. Additional protective measures include implementing application whitelisting policies to restrict which executables can run on the system, monitoring for suspicious DLL loading activities, and ensuring that all system components are regularly updated with the latest security patches. The vulnerability demonstrates the critical importance of proper system configuration management and highlights the need for regular security assessments of system PATH configurations to prevent similar privilege escalation vulnerabilities from being exploited in other software applications.