CVE-2011-1176 in mpm-itk
Summary
by MITRE
The configuration merger in itk.c in the Steinar H. Gunderson mpm-itk Multi-Processing Module 2.2.11-01 and 2.2.11-02 for the Apache HTTP Server does not properly handle certain configuration sections that specify NiceValue but not AssignUserID, which might allow remote attackers to gain privileges by leveraging the root uid and root gid of an mpm-itk process.
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Analysis
by VulDB Data Team • 10/21/2021
The vulnerability identified as CVE-2011-1176 resides within the mpm-itk Multi-Processing Module for Apache HTTP Server, specifically in the itk.c configuration merger component. This module operates as a process-based multi-processing module that allows Apache to run under different user privileges for each child process, enhancing security through process isolation. The flaw manifests when certain configuration sections contain NiceValue directives without corresponding AssignUserID specifications, creating a critical privilege escalation vector. The vulnerability is particularly concerning because it leverages the inherent root privileges of the mpm-itk process to potentially grant unauthorized access to elevated system privileges.
The technical implementation flaw stems from improper handling of configuration parsing within the itk.c module where the configuration merger fails to validate the consistency between NiceValue and AssignUserID directives. When a NiceValue is specified without an accompanying AssignUserID, the module does not properly enforce the requirement for user ID assignment, creating a scenario where the process maintains elevated privileges unnecessarily. This misconfiguration allows attackers to manipulate the process behavior and potentially escalate privileges to root level access. The vulnerability operates at the system call level where process creation and privilege management occur, making it particularly dangerous in environments where Apache runs with root privileges during startup.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential full system compromise. Attackers can exploit this weakness by crafting specific Apache configuration directives that leverage the root uid and root gid of the mpm-itk process, effectively bypassing normal Unix permission controls. This vulnerability aligns with CWE-276, which addresses incorrect default permissions, and represents a classic case of insufficient privilege management in process-based web server modules. The attack surface is particularly large given that many Apache installations use mpm-itk for security isolation, and the vulnerability can be exploited remotely through configuration modifications or by manipulating existing configuration files.
Mitigation strategies for CVE-2011-1176 require immediate attention to configuration management practices and system hardening. Organizations should ensure that all configuration sections containing NiceValue directives also include explicit AssignUserID specifications to prevent the privilege escalation path. The recommended approach involves implementing strict configuration validation procedures and regular auditing of Apache configuration files to identify and correct inconsistent directive combinations. Additionally, system administrators should consider upgrading to patched versions of mpm-itk module, as the vulnerability was addressed in subsequent releases. The remediation process should also include implementing principle of least privilege configurations where Apache processes run with minimal necessary privileges, reducing the impact scope of potential exploitation. Security monitoring should be enhanced to detect anomalous configuration changes that might indicate exploitation attempts, and access controls should be tightened around Apache configuration files to prevent unauthorized modifications that could trigger this vulnerability.