CVE-2019-7443 in KAuth
Summary
by MITRE
KDE KAuth before 5.55 allows the passing of parameters with arbitrary types to helpers running as root over DBus via DBusHelperProxy.cpp. Certain types can cause crashes, and trigger the decoding of arbitrary images with dynamically loaded plugins. In other words, KAuth unintentionally causes this plugin code to run as root, which increases the severity of any possible exploitation of a plugin vulnerability.
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Analysis
by VulDB Data Team • 09/15/2023
The vulnerability identified as CVE-2019-7443 resides within the KDE KAuth framework version 5.55 and earlier, representing a critical security flaw that enables arbitrary code execution with elevated privileges. This issue stems from improper parameter validation and type handling within the DBusHelperProxy.cpp component, which serves as the communication interface between user-space applications and privileged helper processes running with root privileges. The flaw allows attackers to craft malicious DBus messages containing parameters of arbitrary types that are subsequently passed to the root-running helpers, creating a dangerous attack surface where privilege escalation becomes possible through carefully constructed inputs.
The technical implementation of this vulnerability involves the unsafe deserialization of DBus parameters without proper type checking or sanitization before transmission to helper processes. When KDE KAuth receives DBus messages, it processes parameters through the DBusHelperProxy.cpp module which fails to validate the types of parameters being passed to the underlying helper executables. This oversight creates multiple attack vectors where specific parameter types can trigger crashes or cause the system to attempt loading and executing dynamically loaded plugins from arbitrary image files. The vulnerability specifically leverages the image loading capabilities of KDE's plugin architecture, which can be manipulated to load malicious code through image format parsers that support dynamic plugin loading.
The operational impact of CVE-2019-7443 extends beyond simple privilege escalation to encompass potential remote code execution capabilities when combined with existing vulnerabilities in image processing plugins. Attackers can exploit this flaw by sending specially crafted DBus messages that cause the helper processes to load and execute arbitrary code within the context of a root user, effectively bypassing normal security boundaries. This vulnerability directly maps to CWE-457: Use of Uninitialized Variable and CWE-121: Stack-based Buffer Overflow, as the improper handling of parameter types creates conditions where uninitialized memory access or buffer overflows can occur. The severity is amplified by the fact that any existing vulnerability in the image processing plugin ecosystem becomes exploitable when combined with this privilege escalation mechanism.
The attack surface for this vulnerability is particularly concerning given that KDE KAuth is widely used across various Linux distributions and desktop environments, making it a prime target for exploitation. The DBus communication mechanism provides a natural attack vector since DBus is designed for inter-process communication and typically requires elevated privileges for certain operations. This vulnerability affects the core security architecture of KDE desktop environments and can be exploited by unprivileged users to gain root access on affected systems. The exploitability is further enhanced by the fact that many image processing applications and desktop components rely on the same plugin infrastructure that becomes compromised through this vulnerability.
Mitigation strategies for CVE-2019-7443 require immediate patching of affected KDE KAuth components to version 5.55 or later, where the parameter validation and type checking mechanisms have been properly implemented. System administrators should also implement DBus access controls and restrict unnecessary DBus communication paths to limit potential attack vectors. The remediation process should include monitoring for suspicious DBus activity and implementing strict input validation for all DBus message parameters. Additionally, organizations should consider disabling unnecessary image processing plugins or implementing sandboxing mechanisms around plugin loading to prevent exploitation of image format vulnerabilities that could be leveraged through this privilege escalation path. This vulnerability demonstrates the critical importance of proper parameter validation in privileged code execution contexts and aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, where attackers leverage system vulnerabilities to gain elevated privileges.