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CriticalFix available

ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

Products
Kernel
Affected versions
Not specified
Fixed versions
6.1.175, 6.12.84, 6.18.25, 6.6.136, 7.0.2
CVEs
CVE-2026-31705
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 07:01 UTC · Revision 1

Source evidence

ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

core-osv · Original source

Published 1 May 2026, 13:56 UTC

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

osv:CVE-2026-31705

Kernel

Fixed versions: 6.1.175, 6.6.136, 6.12.84, 6.18.25, 7.0.2

Complete source record
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  "url": "https://osv.dev/vulnerability/CVE-2026-31705",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f (\"ksmbd: fix potencial OOB in get_file_all_info() for compound requests\") and commit fda9522ed6af (\"ksmbd: fix OOB write in QUERY_INFO for compound requests\"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.",
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      "modified": "2026-10-28T02:30:26.629325791Z",
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  "source_id": "core-osv",
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  "published_at": "2026-05-01T13:56:03.896+00:00"
}