Answer in brief
CVE-2026-64398 records a Unknown severity vulnerability in ksmbd: add a permission check for FSCTL_SET_ZERO_DATA. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <25377f369688dd0bd814dc8965ed26d44238ecaa || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <3072d82461f498c85daea8766e9d8bfbada31605 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <ca53bb17f4e8232cfaece3953d3cef62c559b039 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <deffa929086d7902e30918adf3dd27ccfe9c08b1 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <3320ba068198adc144c89d6661b805acce01735b | 25377f369688dd0bd814dc8965ed26d44238ecaa, 3072d82461f498c85daea8766e9d8bfbada31605, ca53bb17f4e8232cfaece3953d3cef62c559b039, 57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7, deffa929086d7902e30918adf3dd27ccfe9c08b1, 3320ba068198adc144c89d6661b805acce01735b |
| Linux/Linuxgeneric | 5.15 | Not reported |
Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-64398 records a Unknown severity vulnerability in ksmbd: add a permission check for FSCTL_SET_ZERO_DATA. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <25377f369688dd0bd814dc8965ed26d44238ecaa || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <3072d82461f498c85daea8766e9d8bfbada31605 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <ca53bb17f4e8232cfaece3953d3cef62c559b039 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <deffa929086d7902e30918adf3dd27ccfe9c08b1 || >=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <3320ba068198adc144c89d6661b805acce01735b | 25377f369688dd0bd814dc8965ed26d44238ecaa, 3072d82461f498c85daea8766e9d8bfbada31605, ca53bb17f4e8232cfaece3953d3cef62c559b039, 57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7, deffa929086d7902e30918adf3dd27ccfe9c08b1, 3320ba068198adc144c89d6661b805acce01735b |
| Linux/Linuxgeneric | 5.15 | Not reported |
Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.