{"id":"CVE-2026-72380","summary":"xen/pvcalls: bound backend response req_id before indexing rsp[]","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxen/pvcalls: bound backend response req_id before indexing rsp[]\n\npvcalls_front_event_handler() takes req_id directly from the\nbackend-supplied ring response and uses it to index the fixed-size\nbedata-\u003ersp[] array for a memcpy() and a store, with no range check. A\nmalicious or buggy backend can set req_id past PVCALLS_NR_RSP_PER_RING\nand drive an out-of-bounds write past the bedata allocation.\n\nreq_id was also declared int while the wire field rsp-\u003ereq_id is u32, so\na range check on the signed value alone is insufficient: a backend\nreq_id of 0xffffffff becomes -1, passes a \u003e= PVCALLS_NR_RSP_PER_RING\ntest and indexes bedata-\u003ersp[-1]. Declare req_id as u32 so a single\nbound covers both ends.\n\nA backend that sends an out-of-range req_id has violated the wire\nprotocol, so rather than silently dropping the response, log once and\nstop trusting the backend: set bedata-\u003edisabled. The event handler then\nignores further responses, and the request paths that wait for a\nresponse return -EIO instead of blocking forever. This mirrors the\nfatal-error handling xen-netback uses (xenvif_fatal_tx_err()).\n\nThe pvcalls frontend currently trusts its backend, so this is not a\nclassic-Xen security issue, but it matters for hardening PV frontends\nagainst malicious backends (confidential and disaggregated deployments).","modified":"2026-08-16T03:48:27.762983231Z","published":"2026-08-15T05:56:12.866Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72380.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/d1297a9e2fd6ce08678b370d41bc980ca798f809"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d33846c8dcc06b83b7acdeac1e8bfbb5c0c26cb2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72380.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72380"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2195046bfd69e487d9a76dc47840f15c8412840c"},{"fixed":"d1297a9e2fd6ce08678b370d41bc980ca798f809"},{"fixed":"d33846c8dcc06b83b7acdeac1e8bfbb5c0c26cb2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72380.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.15.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72380.json"}}],"schema_version":"1.9.0"}