CVE-2017-15129 in Linux
Summary
by MITRE
A use-after-free vulnerability was found in network namespaces code affecting the Linux kernel before 4.14.11. The function get_net_ns_by_id() in net/core/net_namespace.c does not check for the net::count value after it has found a peer network in netns_ids idr, which could lead to double free and memory corruption. This vulnerability could allow an unprivileged local user to induce kernel memory corruption on the system, leading to a crash. Due to the nature of the flaw, privilege escalation cannot be fully ruled out, although it is thought to be unlikely.
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Analysis
by VulDB Data Team • 01/20/2023
The vulnerability identified as CVE-2017-15129 represents a critical use-after-free condition within the Linux kernel's network namespace implementation that affects versions prior to 4.14.11. This flaw exists in the network namespace subsystem where the kernel manages isolated network environments for processes. The vulnerability specifically resides in the get_net_ns_by_id() function located in the net/core/net_namespace.c source file, which handles the retrieval of network namespace objects by their identifier. The issue stems from insufficient validation of the reference count mechanism that governs network namespace objects, creating a scenario where memory management can become corrupted through improper object lifecycle handling.
The technical exploitation of this vulnerability occurs when the kernel's network namespace management code fails to properly verify the net::count value after locating a peer network namespace within the netns_ids idr (integer descriptor repository) data structure. This oversight allows an attacker to manipulate the reference counting mechanism in such a way that a network namespace object can be freed while still being referenced elsewhere in the kernel's memory management system. When the kernel attempts to access or free the same memory region twice, it results in a double free condition that can cause memory corruption and ultimately lead to system crashes. The flaw operates at the kernel level where memory management and object lifecycle control are paramount for system stability and security.
The operational impact of CVE-2017-15129 extends beyond simple system crashes to potentially enable privilege escalation scenarios, despite the low probability of successful exploitation. An unprivileged local user can leverage this vulnerability to manipulate kernel memory structures through carefully crafted network namespace operations, potentially leading to arbitrary code execution. The vulnerability's classification aligns with CWE-416, which addresses use-after-free conditions, and demonstrates characteristics consistent with the ATT&CK technique T1068, which involves exploiting legitimate credentials to execute malicious code with elevated privileges. The nature of the flaw makes it particularly dangerous because it operates within the kernel's core memory management subsystem, where unauthorized access can have far-reaching consequences for system integrity and security posture.
Mitigation strategies for CVE-2017-15129 primarily focus on upgrading the Linux kernel to version 4.14.11 or later, where the vulnerability has been patched through proper reference counting validation in the get_net_ns_by_id() function. System administrators should implement comprehensive patch management processes to ensure all affected systems receive timely updates. Additional protective measures include monitoring for unusual network namespace operations and implementing kernel hardening techniques such as stack canaries, address space layout randomization, and kernel module signing. Organizations should also consider implementing network segmentation and access controls to limit potential exploitation vectors, while maintaining regular security audits to detect any anomalous behavior in kernel memory management that could indicate attempted exploitation of similar vulnerabilities. The patch addresses the root cause by ensuring proper validation of reference counts before object access, preventing the double free condition that enables the memory corruption.