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CVE-2026-31712— ksmbd: require minimum ACE size in smb_check_perm_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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksmbd的smb_check_perm_dacl()函数中ACE大小验证不足，可能导致越界读取。

CVSS 8.3 · High EPSS 0.32% · P24

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 282cbbb476b9f35793452bc461934af4c7eca169 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< f20adc4ef7428bc485ee83fd1a592252fb87718b affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 325d4ac11f526cb8964cff14548ccf02d8c756d8 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 90089584b2e25c4510b7b987387b4405f0673ece affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 151b1799861fde38087c08f613abc2843ef597b0 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< d07b26f39246a82399661936dd0c853983cfade7 affected
5.15 affected
… +8 more rows
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I. Basic Information for CVE-2026-31712

Vulnerability Information
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Vulnerability Title
ksmbd: require minimum ACE size in smb_check_perm_dacl()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: require minimum ACE size in smb_check_perm_dacl() Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES * 4 bytes). Tighten both loops to require ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE which is the smallest valid on-wire ACE layout (4-byte header + 4-byte access_req + 8-byte sid base with zero sub-auths). Also reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES before letting compare_sids() dereference sub_auth[] entries. parse_sec_desc() already enforces an equivalent check (lines 441-448); smb_check_perm_dacl() simply grew weaker validation over time. Reachability: authenticated SMB client with permission to set an ACL on a file. On a subsequent CREATE against that file, the kernel walks the stored DACL via smb_check_perm_dacl() and triggers the OOB read. Not pre-auth, and the OOB read is not reflected to the attacker, but KASAN reports and kernel state corruption are possible.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksmbd的smb_check_perm_dacl()函数中ACE大小验证不足，可能导致越界读取。
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 ~ 282cbbb476b9f35793452bc461934af4c7eca169 -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-31712

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III. Intelligence Information for CVE-2026-31712

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Patches & Fixes for CVE-2026-31712 (7)

Same Patch Batch · Linux · 2026-05-01 · 146 CVEs total

CVE-2026-43037 9.8 CRITICAL ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
CVE-2026-43038 9.8 CRITICAL ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
CVE-2026-43039 9.8 CRITICAL net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch
CVE-2026-43011 9.8 CRITICAL net/x25: Fix potential double free of skb
CVE-2026-31705 9.8 CRITICAL ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment
CVE-2026-31718 9.8 CRITICAL ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
CVE-2026-43048 8.8 HIGH HID: core: Mitigate potential OOB by removing bogus memset()
CVE-2026-31739 8.8 HIGH crypto: tegra - Add missing CRYPTO_ALG_ASYNC
CVE-2026-31735 8.8 HIGH iommupt: Fix short gather if the unmap goes into a large mapping
CVE-2026-31773 8.8 HIGH Bluetooth: SMP: derive legacy responder STK authentication from MITM state
CVE-2026-31717 8.8 HIGH ksmbd: validate owner of durable handle on reconnect
CVE-2026-43018 8.8 HIGH Bluetooth: hci_event: fix potential UAF in hci_le_remote_conn_param_req_evt
CVE-2026-31709 8.8 HIGH smb: client: validate the whole DACL before rewriting it in cifsacl
CVE-2026-31706 8.8 HIGH ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl()
CVE-2026-31779 8.1 HIGH wifi: iwlwifi: mvm: fix potential out-of-bounds read in iwl_mvm_nd_match_info_handler()
CVE-2026-31771 8.1 HIGH Bluetooth: hci_event: move wake reason storage into validated event handlers
CVE-2026-43051 8.1 HIGH HID: wacom: fix out-of-bounds read in wacom_intuos_bt_irq
CVE-2026-31708 8.1 HIGH smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
CVE-2026-31772 7.8 HIGH Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync
CVE-2026-43019 7.8 HIGH Bluetooth: hci_conn: fix potential UAF in set_cig_params_sync

Showing top 20 of 146 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31712

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