CVE-2026-63928 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
USB: serial: omninet: fix memory corruption with small endpoint
Make sure that the bulk-out buffers are at least as large as the hardcoded transfer size to avoid user-controlled slab corruption should a malicious device report a smaller endpoint max packet size than expected.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides within the Linux kernel's USB subsystem, specifically affecting the omninet serial driver implementation. The flaw manifests as a memory corruption issue that occurs when handling USB bulk-out transfers through the omninet driver interface. The vulnerability stems from inadequate buffer size validation during USB endpoint configuration processing where the system fails to properly verify that bulk-out buffers meet minimum size requirements dictated by hardcoded transfer parameters.
The technical root cause involves improper bounds checking within the USB serial driver's endpoint handling logic. When a malicious USB device presents an endpoint descriptor reporting a maximum packet size smaller than the driver's hardcoded expected transfer size, the system proceeds with insufficient buffer allocation. This creates a slab corruption scenario where user-controlled data from the malformed USB device can overwrite adjacent memory regions within the kernel's memory management structures. The vulnerability represents a classic buffer overflow condition that exploits improper input validation mechanisms.
From an operational security perspective, this vulnerability presents significant risks to systems running Linux kernels with USB serial support enabled. An attacker with physical access to a target system or the ability to present malicious USB devices could exploit this flaw to achieve arbitrary code execution within kernel space. The memory corruption affects the kernel's slab allocator, potentially leading to system crashes, data corruption, or privilege escalation opportunities. The vulnerability is particularly concerning in environments where untrusted USB devices might be connected, such as public kiosks, shared workstations, or industrial control systems.
The flaw aligns with CWE-129 and CWE-787 categories within the Common Weakness Enumeration framework, specifically addressing improper input validation and out-of-bounds writes in kernel memory management contexts. From an attacker's methodology perspective, this vulnerability maps to ATT&CK technique T1059.006 for execution through kernel-level code injection and T1211 for privilege escalation via memory corruption. The attack vector requires physical device access or the ability to present malicious USB hardware that can manipulate endpoint descriptors during enumeration.
Mitigation strategies should focus on implementing proper buffer size validation before endpoint configuration processing, ensuring that all bulk-out buffers meet or exceed hardcoded transfer size requirements regardless of reported endpoint capabilities. Kernel updates addressing this specific issue provide the primary defense mechanism, while additional protective measures include disabling unnecessary USB serial drivers, implementing USB device whitelisting policies, and monitoring for anomalous USB endpoint descriptor configurations. Organizations should prioritize patching affected systems and consider runtime protections such as kernel module signing enforcement to prevent exploitation of similar vulnerabilities in unpatched systems.