CVE-2026-64398 Affecting linux-6.12 package, versions <6.12.100-1~deb12u1
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-ECHOLATEST-LINUX612-18579244
- published7 Aug 2026
- disclosed25 Jul 2026
Introduced: 25 Jul 2026
CVE-2026-64398 (opens in a new tab)How to fix?
Upgrade Echo:latest linux-6.12 to version 6.12.100-1~deb12u1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream linux-6.12 package and not the linux-6.12 package as distributed by Echo.
See How to fix? for Echo:latest relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: add a permission check for FSCTL_SET_ZERO_DATA
FSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via ksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after checking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no per-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES still yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of FILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it O_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with KASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle zeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to (6/6; a FILE_READ_DATA-only handle was correctly denied).
This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE"). Because SET_ZERO_DATA writes data (not an attribute), require FILE_WRITE_DATA.
References
- https://advisory.echohq.com/cve/CVE-2026-64398
- https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa
- https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605
- https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b
- https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7
- https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039
- https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1