Out-of-bounds Write Affecting kernel6.18-tools-debuginfo package, versions <1:6.18.39-79.141.amzn2023
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-AMZN2023-KERNEL618TOOLSDEBUGINFO-18907100
- published18 Aug 2026
- disclosed25 Jul 2026
Introduced: 25 Jul 2026
NewCVE-2026-64293 (opens in a new tab)How to fix?
Upgrade Amazon-Linux:2023 kernel6.18-tools-debuginfo to version 1:6.18.39-79.141.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2045.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel6.18-tools-debuginfo package and not the kernel6.18-tools-debuginfo package as distributed by Amazon-Linux.
See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read
The bound-check in iommufd_veventq_fops_read() for the normal vEVENT path uses sizeof(hdr) where the surrounding code uses sizeof(*hdr):
if (!vevent_for_lost_events_header(cur) &&
sizeof(hdr) + cur->data_len > count - done) {
hdr is declared as struct iommufd_vevent_header *, so sizeof(hdr) evaluates to the size of the pointer. Surrounding code uses sizeof(*hdr) consistently:
if (done >= count || sizeof(*hdr) > count - done) {
...
if (copy_to_user(buf + done, hdr, sizeof(*hdr))) {
...
done += sizeof(*hdr);
struct iommufd_vevent_header is currently 8 bytes (two __u32 fields, flags and sequence), so on 64-bit (sizeof(void *) == 8) the two expressions happen to be equal and the check works as intended.
On 32-bit (sizeof(void *) == 4) the check under-counts the header by 4 bytes: a vEVENT whose data_len causes 8 + cur->data_len to exceed count - done while 4 + cur->data_len does not will pass the check, then the loop will copy_to_user 8 bytes of header followed by data_len bytes of payload, writing past the user-supplied buffer.
It is also a latent bug for any future expansion of struct iommufd_vevent_header beyond sizeof(void *) on 64-bit; the check should not depend on the type happening to match the host pointer width.
Use sizeof(*hdr) to match the rest of the function and the actual amount that will be copied.