CVE-2026-80826 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
USB: c67x00: fix use-after-free in c67x00_add_iso_urb()
When TD creation fails for the last packet of an isochronous URB, c67x00_add_iso_urb() gives the URB back before updating the endpoint scheduling state.
c67x00_giveback_urb() frees the URB private data, and the completion callback may release the final URB reference. The following accesses to urbp->ep_data, urb->interval, and urbp->cnt can therefore use freed memory.
Update next_frame and cnt before giving back the failed final packet, making the giveback the last operation that uses the URB and its private data.
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Analysis
by VulDB Data Team • 09/04/2026
The Linux kernel vulnerability identified in the c67x00 USB driver represents a critical use-after-free condition within the isochronous Universal Resource Block handling logic. This flaw specifically manifests during the processing of transfer descriptors when creation fails for the final packet of an isochronous URB. The root cause lies in the incorrect ordering of operations within the c67x00_add_iso_urb function, where the driver prematurely returns control to the core USB subsystem by invoking giveback mechanisms before updating essential endpoint scheduling state variables. This sequence error creates a window where memory that should remain valid is released while still being referenced for subsequent updates or accesses.
From a technical perspective, the vulnerability stems from the interaction between URB completion callbacks and private data management. When c67x00_giveback_urb is executed due to the failure of TD creation, it frees the URB's private data structure immediately. However, if the completion callback subsequently releases the final reference count for that same URB object, any subsequent code path attempting to access fields such as urbp->ep_data, urb->interval, or urbp->cnt will operate on memory addresses that have already been deallocated by the kernel's slab allocator. This constitutes a classic use-after-free scenario where stale pointers are dereferenced after their underlying storage has been reclaimed and potentially reallocated for other purposes.
The operational impact of this vulnerability is severe, as it can lead to arbitrary code execution or system instability depending on how the freed memory is reused by subsequent kernel operations. An attacker with local access who can trigger specific USB device interactions might exploit this race condition to corrupt kernel heap structures. This corruption could result in a denial of service through kernel panics or crashes, and more critically, it may allow for privilege escalation if the overwritten data influences control flow pointers or security-critical state variables within the kernel space. The isochronous nature of USB transfers makes these events potentially frequent under high-bandwidth device usage, increasing the attack surface.
This vulnerability aligns with CWE-416, which describes use-after-free errors where a pointer references memory that has been freed and may be reused for other purposes. In terms of offensive security frameworks, this flaw facilitates techniques associated with ATT&CK T1059 Command and Scripting Interpreter or more broadly kernel exploitation vectors like privilege escalation via heap corruption. The lack of proper state synchronization before resource release is a common pattern in driver development that leads to such memory safety violations.
To mitigate this vulnerability, the fix involves reordering the operations within c67x00_add_iso_urb so that critical endpoint scheduling updates are performed prior to invoking any giveback routines. Specifically, updating next_frame and cnt before giving back the failed final packet ensures that all necessary state modifications occur while the URB and its private data remain valid. This adjustment guarantees that the giveback operation becomes the last action utilizing these resources, thereby preventing access to freed memory. System administrators should ensure their Linux kernels are updated with patches addressing this specific c67x00 driver issue, particularly for systems relying on TI C67x00 USB controllers in isochronous transfer modes.