CVE-2026-99063: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: dm ioctl: don't let data_start run past the buffer struct dm_ioctl has seven bytes of trailing padding, so the smallest buffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data), is seven bytes shorter than sizeof(struct dm_ioctl). get_result_buffer() sets data_start to sizeof(struct dm_ioctl) without looking at how big the buffer actually is. Ask for the minimum and data_start ends up seven bytes past the end. Callers add it to data_size, and ctl_ioctl() copies that much back to userspace: BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0 Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140 ctl_ioctl+0x5e3/0xcb0 dm_ctl_ioctl+0x25/0x40 allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31) A DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the seven bytes that leak are whatever sat next to the allocation. Clamp data_start to the buffer size. Note that this is not a security bug because the out-of-bounds read can only be triggered by root.

Metrics

EPSS Probability

0.17%

6.1th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < aaa93e41ae308ad9ff9d9ba3296a0d0f4d45bad3; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < f171054f3c4cfc4dc0cb622ec5b15793e5f23029; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < afe80ec31464f4c54cc1bc658753bc14cb14bd6c; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < 98195e822343a656b92e235847ab3e72b1a3f920; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < e5c3f3d8935ecc64c962fb66e6a86dbf79218f61; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < 5680b6fb3054677d4ee65d3baba24b649f1b430e; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < 725b49c689bbb29ef740b0d6b5ea9390baa9a695; >= 76c072b48e39e9291fbf02d6c912cf27d65e093d, < 9b3fcf519d370df94a56f3b272d9eddffffa5be8
Linux	Linux	2.6.25

References

Timeline

Published: Oct 23, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-99063?

In the Linux kernel, the following vulnerability has been resolved: dm ioctl: don't let data_start run past the buffer struct dm_ioctl has seven bytes of trailing padding, so the smallest buffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data), is seven bytes shorter than sizeof(struct dm_ioctl). get_result_buffer() sets data_start to sizeof(struct dm_ioctl) without looking at how big the buffer actually is. Ask for the minimum and data_start ends up seven bytes past the end. Callers add it to data_size, and ctl_ioctl() copies that much back to userspace: BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0 Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140 ctl_ioctl+0x5e3/0xcb0 dm_ctl_ioctl+0x25/0x40 allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31) A DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the seven bytes that leak are whatever sat next to the allocation. Clamp data_start to the buffer size. Note that this is not a security bug because the out-of-bounds read can only be triggered by root.

How severe is CVE-2026-99063?

Severity scoring for CVE-2026-99063 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-99063?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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