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CVE-2026-68100— ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.6.148之前版本、6.12.101之前版本、6.18.42之前版本和7.1.6之前版本存在安全漏洞，该漏洞源于ksmbd的set_ntacl_dacl函数在复制ACE时未验证num_subauth，可能导致越界堆读取，进而造成信息泄露或拒绝服务。

CVSS 8.1 · High EPSS 0.43% · P36

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 26cb845e22a00c85bf566337417fa33492395f10 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< e31fada5143784bc05c7ae44c79eed9b7a2e147e affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< fb3dc8e6da46a1ccad1956cda57de29d9b3033e0 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< b6d3cc6a524416dfdb2b47e4bba2e7e20011d056 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 5acbd3012fd4a7ccfebd91ea6f784120084eb897 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d affected
5.15 affected
< 5.15 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-68100

Vulnerability Information
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Vulnerability Title
ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl().
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.6.148之前版本、6.12.101之前版本、6.18.42之前版本和7.1.6之前版本存在安全漏洞，该漏洞源于ksmbd的set_ntacl_dacl函数在复制ACE时未验证num_subauth，可能导致越界堆读取，进而造成信息泄露或拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 ~ 26cb845e22a00c85bf566337417fa33492395f10 -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-68100

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III. Intelligence Information for CVE-2026-68100

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Patches & Fixes for CVE-2026-68100 (4)

Same Patch Batch · Linux · 2026-08-10 · 344 CVEs total

CVE-2026-68156 9.8 CRITICAL libceph: refresh auth->authorizer_buf{,_len} after authorizer update
CVE-2026-68123 9.8 CRITICAL openvswitch: fix GSO userspace truncation underflow
CVE-2026-68117 9.8 CRITICAL tipc: clear sock->sk on the failed-insert path in tipc_sk_create()
CVE-2026-68127 9.8 CRITICAL ila: reload IPv6 header after pskb_may_pull in checksum adjust
CVE-2026-68300 9.8 CRITICAL sctp: auth: verify auth requirement when auth_chunk is NULL
CVE-2026-68136 9.8 CRITICAL net: gro: fix double aggregation of flush-marked skbs
CVE-2026-68137 9.8 CRITICAL net/x25: fix use-after-free in x25_kill_by_neigh()
CVE-2026-68144 9.8 CRITICAL phonet: pep: fix use-after-free in pep_get_sb()
CVE-2026-68302 9.8 CRITICAL amt: re-read skb header pointers after every pull
CVE-2026-68154 9.8 CRITICAL libceph: reject zero bucket types in crush_decode
CVE-2026-68158 9.8 CRITICAL libceph: Fix multiplication overflow in decode_new_up_state_weight()
CVE-2026-68159 9.8 CRITICAL libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE
CVE-2026-68160 9.8 CRITICAL ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()
CVE-2026-68388 9.8 CRITICAL smb/client: handle overlapping allocated ranges in fallocate
CVE-2026-68170 9.8 CRITICAL mptcp: fix stale skb->sk reference on subflow close
CVE-2026-68385 9.8 CRITICAL s390/checksum: Fix csum_partial() without vector facility
CVE-2026-68426 9.8 CRITICAL xfrm: fix stale skb->prev after async crypto steals a GSO segment
CVE-2026-68381 9.8 CRITICAL ksmbd: pin conn during async oplock break notification
CVE-2026-68161 9.8 CRITICAL sctp: close UDP tunnel sockets during netns teardown
CVE-2026-68124 9.6 CRITICAL mctp: serial: handle zero-length frames to prevent rx buffer overflow

Showing top 20 of 344 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-68100

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