CVE-2017-7487 in Linux
Summary
by MITRE
The ipxitf_ioctl function in net/ipx/af_ipx.c in the Linux kernel through 4.11.1 mishandles reference counts, which allows local users to cause a denial of service (use-after-free) or possibly have unspecified other impact via a failed SIOCGIFADDR ioctl call for an IPX interface.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-7487 resides within the Linux kernel's IPX protocol implementation, specifically in the ipxitf_ioctl function located in net/ipx/af_ipx.c. This flaw represents a critical issue affecting kernel versions through 4.11.1, where improper reference count management creates exploitable conditions that can lead to system instability or potential privilege escalation. The vulnerability manifests when a malformed SIOCGIFADDR ioctl call is executed against an IPX interface, triggering a cascade of memory management failures that compromise system integrity.
The technical root cause of this vulnerability stems from inadequate reference counting mechanisms within the IPX network interface handling code. When the ipxitf_ioctl function processes a failed SIOCGIFADDR ioctl call, it fails to properly decrement reference counts for IPX interface structures, creating a scenario where memory allocated to these structures can be freed while still referenced elsewhere in the kernel. This improper reference count handling directly maps to CWE-415, which describes double free vulnerabilities, and CWE-416, which addresses use-after-free conditions. The flaw allows local attackers with access to the system to manipulate the kernel's memory management subsystem through carefully crafted ioctl operations.
The operational impact of CVE-2017-7487 extends beyond simple denial of service, as the use-after-free condition can potentially be exploited to execute arbitrary code within kernel space. Attackers can leverage this vulnerability to cause system crashes, leading to persistent denial of service conditions that can be difficult to detect and recover from. The vulnerability's local nature means that exploitation requires only basic user privileges, making it particularly dangerous in multi-user environments where unprivileged users could potentially disrupt system operations or escalate privileges. The memory corruption aspects of this vulnerability align with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities.
Mitigation strategies for CVE-2017-7487 should prioritize immediate kernel updates to versions 4.11.2 or later, where the reference counting issue has been addressed through proper memory management corrections. System administrators should disable IPX protocol support entirely if the functionality is not required, as this eliminates the attack surface entirely. Additional protective measures include implementing strict access controls on network interface operations, monitoring for suspicious ioctl call patterns, and maintaining comprehensive system logging to detect potential exploitation attempts. The fix implemented in subsequent kernel versions demonstrates proper reference count management through careful decrement operations and validation checks that prevent the conditions leading to memory corruption. Organizations should also consider implementing kernel hardening measures such as stack canaries and address space layout randomization to further reduce the exploitability of similar vulnerabilities.