{"id":"CVE-2026-64293","title":"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 s…","summary":"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 s…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","published":"2026-07-25","updated":"2026-07-27","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64293","references":[{"url":"https://git.kernel.org/stable/c/04a177f91160ee18da98f5689482cf0f589ec869","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/0cdbb97a4dbd69abdd2ab998b4fbc7803d4b0b72","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/be93d186ae88a92e7aa77e122d4e661fa57b1e39","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00162,"epssPercentile":0.05779,"ingestedAt":"2026-07-27T06:16:50.143Z","slug":"CVE-2026-64293","body":"## Overview\n\nIn 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}