CVE-2026-93117
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
usb: fix UAF when probe runs concurrent to dyn ID removal
Dynamic IDs are only guaranteed to be valid when usb_dynids_lock is held, as remove_id_store can free the node. Thus, make a copy in usb_probe_interface. Clarify the documentation that the id parameter is only valid during the probe.
USB serial has the same pattern, but it does not need fixing as the IDs cannot be removed via sysfs.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel contains a use-after-free vulnerability within the USB subsystem specifically affecting the usb_probe_interface function when executed concurrently with dynamic ID removal operations. This flaw arises from an improper handling of shared data structures during device enumeration and driver binding processes. The core issue lies in the assumption that dynamically allocated identifiers remain valid throughout the entire probing lifecycle without adequate synchronization mechanisms to protect against concurrent modifications by other kernel threads or subsystems responsible for managing USB device configurations.
Dynamic IDs are managed through a linked list structure protected by usb_dynids_lock, which ensures thread safety during access and modification operations. However, when probe routines execute concurrently with remove_id_store functions triggered via sysfs interfaces, there exists a race condition where the node containing identifier information can be freed while still being referenced by an ongoing probe operation. This creates a classic use-after-free scenario where memory previously allocated for ID structures is deallocated but subsequently accessed through dangling pointers maintained within the probing context. The vulnerability specifically impacts scenarios where device drivers attempt to match incoming USB devices against dynamically registered identifiers without holding appropriate locks during critical sections of code execution.
The operational impact of this vulnerability includes potential kernel crashes, data corruption, and privilege escalation opportunities for attackers who can trigger concurrent probe and removal operations through physical access or compromised peripheral devices. By manipulating the timing between device insertion events and sysfs-based ID modifications, an attacker could exploit the race condition to execute arbitrary code within kernel space with root-level privileges. This represents a significant security risk particularly in environments where USB devices are frequently added and removed from systems under untrusted conditions such as public computing facilities or IoT deployments involving peripheral management interfaces accessible to non-privileged users.
Mitigation strategies involve implementing proper synchronization mechanisms by copying dynamic ID data structures before accessing them during probe operations rather than maintaining direct references that may become invalid due to concurrent modifications. The fix ensures that usb_probe_interface creates local copies of identifier information while holding the appropriate locks, thereby eliminating dependency on externally managed memory regions whose lifecycle is controlled independently from the probing process. Additionally documentation clarifications emphasize that id parameters passed to probe functions are only valid during execution time and require explicit locking for safe access beyond immediate processing windows.
This vulnerability aligns with CWE-416 which describes use-after-free conditions resulting from improper resource management in concurrent programming contexts where shared data structures lack adequate protection against simultaneous read-write operations by multiple threads of execution. From an ATT&CK perspective, this represents a technique related to privilege escalation through exploitation of kernel-level race conditions that allow attackers to gain unauthorized access to sensitive system resources and potentially establish persistent footholds within compromised environments. The USB serial subsystem exhibits similar architectural patterns but remains unaffected since its identifier management does not expose removal capabilities via sysfs interfaces, thereby preventing the specific attack vector exploited in this vulnerability scenario involving dynamic ID manipulation through user-space controls triggering kernel-level memory operations without proper synchronization safeguards.