{"id":"CVE-2026-64293","state":"PUBLISHED","title":"iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read","description":"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.","publishedAt":"2026-07-25T08:49:31.945Z","updatedAt":"2026-10-19T20:38:22.244Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"04a177f91160ee18da98f5689482cf0f589ec869","versionType":"git"},{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72","versionType":"git"},{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"be93d186ae88a92e7aa77e122d4e661fa57b1e39","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/iommufd/eventq.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/iommufd/eventq.c"]}],"references":["https://git.kernel.org/stable/c/04a177f91160ee18da98f5689482cf0f589ec869","https://git.kernel.org/stable/c/0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72","https://git.kernel.org/stable/c/be93d186ae88a92e7aa77e122d4e661fa57b1e39"],"weaknesses":["CWE-787"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64293.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64293","state":"PUBLISHED","datePublished":"2026-07-25T08:49:31.945Z","dateUpdated":"2026-10-19T20:38:22.244Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.778Z"},"containers":{"cna":{"title":"iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"04a177f91160ee18da98f5689482cf0f589ec869","versionType":"git"},{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72","versionType":"git"},{"version":"e36ba5ab808ef6237c3148d469c8238674230e2b","status":"affected","lessThan":"be93d186ae88a92e7aa77e122d4e661fa57b1e39","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/iommufd/eventq.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/iommufd/eventq.c"]}],"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"}],"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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:52:50.497Z"},"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"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64293","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:38:30.670764Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","type":"CWE","description":"CWE-787 Out-of-bounds Write"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:38:22.244Z"}}]}}}