{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64293", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T15:36:31.778Z", "datePublished": "2026-07-25T08:49:31.945Z", "dateUpdated": "2026-08-17T04:52:50.497Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:52:50.497Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read\n\nThe bound-check in iommufd_veventq_fops_read() for the normal vEVENT\npath uses sizeof(hdr) where the surrounding code uses sizeof(*hdr):\n\n\tif (!vevent_for_lost_events_header(cur) &&\n\t sizeof(hdr) + cur->data_len > count - done) {\n\nhdr is declared as struct iommufd_vevent_header *, so sizeof(hdr)\nevaluates to the size of the pointer. Surrounding code uses\nsizeof(*hdr) consistently:\n\n\tif (done >= count || sizeof(*hdr) > count - done) {\n\t...\n\tif (copy_to_user(buf + done, hdr, sizeof(*hdr))) {\n\t...\n\tdone += sizeof(*hdr);\n\nstruct iommufd_vevent_header is currently 8 bytes (two __u32 fields,\nflags and sequence), so on 64-bit (sizeof(void *) == 8) the two\nexpressions happen to be equal and the check works as intended.\n\nOn 32-bit (sizeof(void *) == 4) the check under-counts the header by\n4 bytes: a vEVENT whose data_len causes 8 + cur->data_len to exceed\ncount - done while 4 + cur->data_len does not will pass the check,\nthen the loop will copy_to_user 8 bytes of header followed by data_len\nbytes of payload, writing past the user-supplied buffer.\n\nIt is also a latent bug for any future expansion of struct\niommufd_vevent_header beyond sizeof(void *) on 64-bit; the check\nshould not depend on the type happening to match the host pointer\nwidth.\n\nUse sizeof(*hdr) to match the rest of the function and the actual\namount that will be copied." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable function is reached through read() on a locally held iommufd vEVENTQ file descriptor; it is not directly network- or device-packet-facing.\nAC:L - On an affected 32-bit deployment, the attacker can deterministically queue an event and choose a count that is one to four bytes too small; no race or uncontrollable condition is required.\nPR:L - No capability check occurs during the vulnerable read, and an unprivileged VMM or user granted an iommufd/vEVENTQ descriptor can invoke it without real init-namespace root.\nUI:N - Exploitation requires only attacker-controlled event generation and a read syscall; no separate victim action is required.\nS:U - The corruption occurs through the host kernel's userspace API and does not itself bypass an IOMMU boundary or demonstrate a guest-to-host escape.\nC:H - The four-byte overwrite can replace a complete pointer or control word in a 32-bit event consumer, potentially enabling code execution and disclosure of arbitrary process secrets.\nI:H - The kernel writes up to four payload bytes beyond the declared userspace buffer, which can corrupt a full 32-bit control value and potentially permit control-flow hijacking.\nA:H - The overwrite can crash a privileged VMM or other event-consuming service, and controllable event generation permits the condition to be triggered repeatedly." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/iommu/iommufd/eventq.c" ], "versions": [ { "version": "e36ba5ab808ef6237c3148d469c8238674230e2b", "lessThan": "04a177f91160ee18da98f5689482cf0f589ec869", "status": "affected", "versionType": "git" }, { "version": "e36ba5ab808ef6237c3148d469c8238674230e2b", "lessThan": "0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72", "status": "affected", "versionType": "git" }, { "version": "e36ba5ab808ef6237c3148d469c8238674230e2b", "lessThan": "be93d186ae88a92e7aa77e122d4e661fa57b1e39", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/iommu/iommufd/eventq.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.39", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.4", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "6.18.39" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.1.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/04a177f91160ee18da98f5689482cf0f589ec869" }, { "url": "https://git.kernel.org/stable/c/0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72" }, { "url": "https://git.kernel.org/stable/c/be93d186ae88a92e7aa77e122d4e661fa57b1e39" } ], "title": "iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read", "x_generator": { "engine": "bippy-1.2.0" } } } }