{"id":"CVE-2026-13216","summary":"Out-of-bounds stack write in Zephyr virtio PCI driver from unvalidated device-supplied capability length","details":"The virtio PCI driver (drivers/virtio/virtio_pci.c) parses a device's PCI capability list during driver initialization. In virtio_pci_read_cap() the device-supplied capability length byte cap_len (read from PCI config space via pcie_conf_read()) was only checked with assert(tmp.cap_len == cap_struct_size). That assert resolves to __ASSERT_NO_MSG(), gated by CONFIG_ASSERT, which defaults off in production builds, so the value reached the copy logic completely unvalidated.\n\nThe length then drives a loop that copies extra capability dwords into a fixed-size stack buffer supplied by the caller. A cap_len below the 24-byte base struct virtio_pci_cap underflows the unsigned extra_data_words count to a near-SIZE_MAX value, producing an effectively unbounded stack write; a cap_len above the caller's buffer (up to 255) writes up to roughly 228 bytes of device-controlled data past the buffer. Both are out-of-bounds writes of attacker-controlled content executed in kernel mode during boot-time device probe.\n\nThe input originates from the virtio device. In the common deployment where Zephyr runs as a guest under a hypervisor, the device backend is the host, which already fully outranks the guest, so the bug yields no privilege escalation. The exploitable case is a virtio device that is untrusted relative to the Zephyr kernel — an untrusted or physical/passthrough virtio PCIe device on a bare-metal system, or a confidential-computing posture where the guest must defend against the host — where a malicious device can corrupt the kernel stack and potentially achieve code execution or a crash.\n\nThe fix replaces the compiled-out assert with a runtime range check rejecting cap_len outside [sizeof(struct virtio_pci_cap), cap_struct_size] before any arithmetic or copy.","aliases":["GHSA-qrh3-4mvv-w667"],"modified":"2026-08-28T14:32:59.484571Z","published":"2026-08-25T16:05:36.964Z","database_specific":{"cna_assigner":"zephyr","cwe_ids":["CWE-787"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/13xxx/CVE-2026-13216.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/13xxx/CVE-2026-13216.json"},{"type":"ADVISORY","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-qrh3-4mvv-w667"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-13216"},{"type":"FIX","url":"https://github.com/zephyrproject-rtos/zephyr/commit/d98dacee24ad10c972d3b7281c9009d82ed351c9"},{"type":"PACKAGE","url":"https://github.com/zephyrproject-rtos/zephyr"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/zephyrproject-rtos/zephyr","events":[{"introduced":"413b789deb391d3a37d06b463288a5fe765ee57e"},{"fixed":"d98dacee24ad10c972d3b7281c9009d82ed351c9"}],"database_specific":{"extracted_events":[{"introduced":"4.2.0"},{"fixed":"4.4.2"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v4.4.0","v4.4.0-rc3","v4.4.0-rc2","v4.4.0-rc1","v4.3.0","v4.3.0-rc3","v4.3.0-rc2","v4.3.0-rc1","v4.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-13216.json","vanir_signatures_modified":"2026-08-28T14:32:59Z","vanir_signatures":[{"digest":{"function_hash":"1237186707346695444725577549462722868","length":1081},"id":"CVE-2026-13216-61325f8a","signature_type":"Function","signature_version":"v1","source":"https://github.com/zephyrproject-rtos/zephyr/commit/d98dacee24ad10c972d3b7281c9009d82ed351c9","target":{"file":"drivers/virtio/virtio_pci.c","function":"virtio_pci_read_cap"},"deprecated":false},{"signature_type":"Line","signature_version":"v1","source":"https://github.com/zephyrproject-rtos/zephyr/commit/d98dacee24ad10c972d3b7281c9009d82ed351c9","target":{"file":"drivers/virtio/virtio_pci.c"},"deprecated":false,"digest":{"threshold":0.9,"line_hashes":["141705835514119104656776053557615128448","220439857227802623790854166360684433939","139873091864490449370155597078729568678","191135874435819231484805636579762432338"]},"id":"CVE-2026-13216-6fc94899"}]}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H"}]}