Bug 2507283 (CVE-2026-64331)

Summary: CVE-2026-64331 kernel: usbip: vudc: fix NULL deref in vep_dequeue()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's usbip virtual USB device controller (vudc). This vulnerability, a NULL pointer dereference, occurs when vep_alloc_request() fails to initialize a vrequest's udc field, causing asynchronous input/output (AIO) cancellations on the FunctionFS path to arrive without a valid UDC reference. A local attacker, or a remote attacker with control over the host's usbip attach operation to a guest, could exploit this to trigger a kernel crash, resulting in a denial of service (DoS).
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Description OSIDB Bzimport 2026-07-25 10:14:28 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usbip: vudc: fix NULL deref in vep_dequeue()

vep_alloc_request() wasn't initializing vrequest->udc, so cancellations
on the FunctionFS AIO path were arriving in vep_dequeue without a valid
UDC reference.

Since vrequest->udc is never actually properly used anywhere, we opt to
remove it, and update vep_dequeue to obtain a reference to the udc with
ep_to_vudc(), consistent with the other vep_ ops.

AFAICT this bug has existed for ~10 years. Seems that nobody has really
stressed the FunctionFS AIO path on usbip's vudc.

I tested this fix in a QEMU aarch64 guest driving FunctionFS endpoints
via AIO. Before the fix, running `usbip attach` from the host would
cause the guest to oops with the following backtrace:

Call trace:
 vep_dequeue+0x1c/0xe4 (P)
 usb_ep_dequeue+0x14/0x20
 ffs_aio_cancel+0x24/0x34
 __arm64_sys_io_cancel+0xb0/0x124
 do_el0_svc+0x68/0x100
 el0_svc+0x18/0x5c
 el0t_64_sync_handler+0x98/0xdc
 el0t_64_sync+0x154/0x158
Comment 1 TEJ RATHI 2026-07-27 08:23:37 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072513-CVE-2026-64331-7a76@gregkh/T