CVE-2026-72380

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

xen/pvcalls: bound backend response req_id before indexing rsp[]

pvcalls_front_event_handler() takes req_id directly from the

backend-supplied ring response and uses it to index the fixed-size

bedata->rsp[] array for a memcpy() and a store, with no range check. A

malicious or buggy backend can set req_id past PVCALLS_NR_RSP_PER_RING

and drive an out-of-bounds write past the bedata allocation.

req_id was also declared int while the wire field rsp->req_id is u32, so

a range check on the signed value alone is insufficient: a backend

req_id of 0xffffffff becomes -1, passes a >= PVCALLS_NR_RSP_PER_RING

test and indexes bedata->rsp[-1]. Declare req_id as u32 so a single

bound covers both ends.

A backend that sends an out-of-range req_id has violated the wire

protocol, so rather than silently dropping the response, log once and

stop trusting the backend: set bedata->disabled. The event handler then

ignores further respons

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References