CVE-2026-98495 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
net: arp: terminate device name before lookup
The ARP ioctl copies a user-provided struct arpreq into a stack object. Its arp_dev field may contain IFNAMSIZ bytes without a NUL terminator.
Such input is passed to dev_get_by_name_rcu() or __dev_get_by_name(), where strcmp() can read past the end of the stack object when a matching alternative interface name exists.
Terminate the field before the lookup to prevent the out-of-bounds read.
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Analysis
by VulDB Data Team • 10/18/2026
The identified vulnerability resides within the Address Resolution Protocol implementation in the Linux kernel, specifically affecting the handling of user-space requests via ioctl interfaces. The core issue stems from an improper boundary check during the processing of struct arpreq data structures provided by unprivileged or privileged users. When a system call is made to manipulate ARP tables, the kernel copies the user-provided structure into a stack-allocated object without ensuring that all string fields are properly null-terminated. Specifically, the arp_dev field, which stores the name of the network interface associated with the ARP entry, may contain up to IFNAMSIZ bytes of data but lacks a guaranteed NUL terminator at its end if the user input does not explicitly include one. This oversight creates a scenario where subsequent string operations assume valid termination points that do not exist within the allocated memory bounds.
The technical flaw manifests when this malformed structure is passed to internal kernel functions such as dev_get_by_name_rcu or __dev_get_by_name, which are responsible for resolving network interface names to their corresponding device structures. These functions utilize strcmp() to compare the provided name against known interface names stored in system tables. Because the input string lacks a NUL terminator and potentially exceeds its allocated buffer size on the stack, strcmp performs an out-of-bounds read operation. This memory access extends beyond the boundaries of the stack object into adjacent memory regions. While this specific instance is classified as an out-of-bounds read rather than a write, it allows for the leakage of kernel memory contents to user space under certain conditions, particularly when a matching alternative interface name exists that triggers the comparison logic before the function returns or errors out due to other constraints.
From a security impact perspective, this vulnerability enables information disclosure through side-channel effects and potential denial of service if the read operation accesses unmapped pages or causes kernel panics due to invalid memory access patterns. The ability to read arbitrary kernel stack contents can aid attackers in bypassing Address Space Layout Randomization by leaking pointers to other critical data structures within the same process context. This aligns with Common Weakness Enumeration category CWE-125, which describes out-of-bounds read vulnerabilities where software reads past the end of a buffer or memory region. Furthermore, this exploitation technique relates to ATT&CK tactic TA0043 Reconnaissance and specifically techniques involving data from local system components for discovery purposes, as it allows an attacker to gather sensitive information about the kernel's internal state without direct write access privileges.
Mitigation strategies primarily involve applying vendor-provided security patches that update the Linux kernel source code to enforce strict string termination before processing user inputs in network-related ioctl handlers. Developers must ensure that all character arrays copied from user space are explicitly null-terminated within their allocated bounds, regardless of whether the input appears complete. Additionally, implementing stricter validation checks on interface name lengths and utilizing safer string handling functions that accept explicit length parameters can prevent such boundary violations. System administrators should prioritize updating kernel packages to versions where this logic has been corrected, thereby eliminating the possibility of stack-based buffer over-reads in network configuration operations.