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CVE-2026-31708— smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path

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smb2_ioctl_query_info()中QUERY_INFO路径未验证响应缓冲区大小，可能导致恶意服务器返回过大的OutputBufferLength导致越界读取。

CVSS 8.1 · High EPSS 0.35% · P27

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux f5778c398713692a16150ae96e5c8270bab8399f< e66bdc0704977ecee667a81d38255b579c2353d0 affected
f5778c398713692a16150ae96e5c8270bab8399f< 9e203dbb5402897c43130fb171a2617008a91f45 affected
f5778c398713692a16150ae96e5c8270bab8399f< 1dd757379997b71a328a4b591ffaf481acd0ead1 affected
f5778c398713692a16150ae96e5c8270bab8399f< a34d456934fe42e4da5d2cc07787bf418bee99c6 affected
f5778c398713692a16150ae96e5c8270bab8399f< ac2f14e4705d020f04e806efa0d49ab8dc2b145f affected
f5778c398713692a16150ae96e5c8270bab8399f< 078fae8f50adebb903ccf2252b44391324571e78 affected
f5778c398713692a16150ae96e5c8270bab8399f< 85fd46ee26a11841c670449508025965f61ce131 affected
f5778c398713692a16150ae96e5c8270bab8399f< a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e affected
… +10 more rows
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I. Basic Information for CVE-2026-31708

Vulnerability Information
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Vulnerability Title
smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path smb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL and the default QUERY_INFO path. The QUERY_INFO branch clamps qi.input_buffer_length to the server-reported OutputBufferLength and then copies qi.input_buffer_length bytes from qi_rsp->Buffer to userspace, but it never verifies that the flexible-array payload actually fits within rsp_iov[1].iov_len. A malicious server can return OutputBufferLength larger than the actual QUERY_INFO response, causing copy_to_user() to walk past the response buffer and expose adjacent kernel heap to userspace. Guard the QUERY_INFO copy with a bounds check on the actual Buffer payload. Use struct_size(qi_rsp, Buffer, qi.input_buffer_length) rather than an open-coded addition so the guard cannot overflow on 32-bit builds.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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smb2_ioctl_query_info()中QUERY_INFO路径未验证响应缓冲区大小，可能导致恶意服务器返回过大的OutputBufferLength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 f5778c398713692a16150ae96e5c8270bab8399f ~ e66bdc0704977ecee667a81d38255b579c2353d0 -
Linux Linux 5.1 -

II. Public POCs for CVE-2026-31708

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III. Intelligence Information for CVE-2026-31708

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Patches & Fixes for CVE-2026-31708 (8)

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-2026-31712 8.3 HIGH ksmbd: require minimum ACE size in smb_check_perm_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-2026-43019 7.8 HIGH Bluetooth: hci_conn: fix potential UAF in set_cig_params_sync
CVE-2026-31772 7.8 HIGH Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_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-2026-31708

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