CVE-2017-1087 in FreeBSD
Summary
by MITRE
In FreeBSD 10.x before 10.4-STABLE, 10.4-RELEASE-p3, and 10.3-RELEASE-p24 named paths are globally scoped, meaning a process located in one jail can read and modify the content of POSIX shared memory objects created by a process in another jail or the host system. As a result, a malicious user that has access to a jailed system is able to abuse shared memory by injecting malicious content in the shared memory region. This memory region might be executed by applications trusting the shared memory, like Squid. This issue could lead to a Denial of Service or local privilege escalation.
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Analysis
by VulDB Data Team • 01/24/2021
The vulnerability described in CVE-2017-1087 represents a critical security flaw in FreeBSD operating systems affecting versions prior to specific stable releases. This issue fundamentally undermines the isolation mechanisms that jails provide, creating a scenario where processes within different jail environments can access each other's shared memory resources. The problem stems from the global scoping of named POSIX shared memory objects, which should theoretically be isolated between jail boundaries but instead remain accessible across system partitions. This flaw directly violates the fundamental security principle of containerization where each jail should maintain its own isolated execution environment. The vulnerability is classified under CWE-284 Access Control, specifically addressing improper access control in shared memory objects that should remain isolated between different security contexts. The issue allows for privilege escalation and denial of service attacks by exploiting the lack of proper boundary enforcement between jail environments.
The technical implementation of this vulnerability occurs through the named POSIX shared memory objects that are created with global scope rather than being properly confined to individual jail contexts. When a process in one jail creates a shared memory object, that object becomes accessible to processes in other jails or even the host system due to the improper scoping mechanism. This access control failure enables malicious users to inject data into shared memory regions that may later be executed by trusted applications such as Squid proxy server. The attack vector specifically targets the shared memory management system where named objects are created using system-wide identifiers instead of jail-specific identifiers, allowing cross-contamination between isolated environments. The flaw enables a malicious user to manipulate shared memory content in ways that could lead to code execution within the context of trusted applications, particularly those that rely on shared memory for data exchange or caching operations.
The operational impact of CVE-2017-1087 extends beyond simple data access violations to encompass serious security compromise scenarios that could affect entire system integrity. A malicious user with access to a jailed environment can leverage this vulnerability to perform local privilege escalation by manipulating shared memory objects that are subsequently processed by applications running with elevated privileges. The potential for denial of service attacks exists when shared memory regions are corrupted or manipulated in ways that cause applications to crash or behave unpredictably. Applications like Squid that utilize shared memory for caching and data processing become particularly vulnerable as they may execute malicious code injected into shared memory regions. The vulnerability also enables information disclosure attacks where sensitive data from other jails or the host system could be accessed through the shared memory interface. This cross-contamination of memory spaces represents a complete breakdown of the security model that jails are designed to enforce, potentially allowing attackers to escalate their privileges or gain access to resources they should not be able to reach.
Mitigation strategies for CVE-2017-1087 require immediate system updates to the patched FreeBSD versions that address the named POSIX shared memory scoping issue. Organizations should ensure all FreeBSD systems are updated to versions 10.4-STABLE, 10.4-RELEASE-p3, or 10.3-RELEASE-p24 which contain the necessary fixes for proper jail boundary enforcement. System administrators should implement additional monitoring of shared memory usage patterns to detect potential exploitation attempts and consider disabling unnecessary shared memory usage in jail environments where possible. The fix implemented in the patched versions addresses the core issue by ensuring that named POSIX shared memory objects are properly scoped to individual jail contexts, preventing cross-contamination between isolated environments. Security teams should also review their jail configurations to ensure proper isolation is maintained and consider implementing additional security controls such as mandatory access controls or extended security policies that further restrict inter-jail communication. The remediation process should include thorough testing of applications that rely on shared memory to ensure compatibility with the fixed implementation while maintaining the security benefits of proper memory isolation. This vulnerability serves as a critical reminder of the importance of proper memory management and access control mechanisms in containerized environments, particularly in systems where multiple security contexts must be maintained.