CVE-2026-31706— Linux kernel 安全漏洞
一分钟漏洞结论
影响对象
Linux Linux
利用判断
尚无明确在野利用证据，仍需结合暴露面评估
建议动作
优先检查厂商安全公告和参考链接中的修复版本；无法立即升级时，限制受影响服务暴露并加强监测。
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smb_inherit_dacl()未验证num_aces值，可能导致堆分配过大且未初始化，以及ACE遍历使用过小的最小大小检查。
影响版本矩阵 10
| 厂商 | 产品 | 版本范围 | 状态 |
|---|---|---|---|
| Linux | Linux | e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 063a7409b0de46d7c770b65bb0338e6fdb3b1f0a |
affected |
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 3e5360b422dd741cb315654a191fa73869a37414 |
affected | ||
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 59c32abaaec9cdd6164811c7e864e72f7554b82d |
affected | ||
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 3e4e2ea2a781018ed5d75f969e3e5606beb66e48 |
affected | ||
5.15 |
affected | ||
< 5.15 |
unaffected | ||
6.12.84≤ 6.12.* |
unaffected | ||
6.18.25≤ 6.18.* |
unaffected | ||
| … +2 条更多 | |||
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一、 漏洞 CVE-2026-31706 基础信息
漏洞信息
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Vulnerability Title
ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl()
来源: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl()
smb_inherit_dacl() trusts the on-disk num_aces value from the parent
directory's DACL xattr and uses it to size a heap allocation:
aces_base = kmalloc(sizeof(struct smb_ace) * num_aces * 2, ...);
num_aces is a u16 read from le16_to_cpu(parent_pdacl->num_aces)
without checking that it is consistent with the declared pdacl_size.
An authenticated client whose parent directory's security.NTACL is
tampered (e.g. via offline xattr corruption or a concurrent path that
bypasses parse_dacl()) can present num_aces = 65535 with minimal
actual ACE data. This causes a ~8 MB allocation (not kzalloc, so
uninitialized) that the subsequent loop only partially populates, and
may also overflow the three-way size_t multiply on 32-bit kernels.
Additionally, the ACE walk loop uses the weaker
offsetof(struct smb_ace, access_req) minimum size check rather than
the minimum valid on-wire ACE size, and does not reject ACEs whose
declared size is below the minimum.
Reproduced on UML + KASAN + LOCKDEP against the real ksmbd code path.
A legitimate mount.cifs client creates a parent directory over SMB
(ksmbd writes a valid security.NTACL xattr), then the NTACL blob on
the backing filesystem is rewritten to set num_aces = 0xFFFF while
keeping the posix_acl_hash bytes intact so ksmbd_vfs_get_sd_xattr()'s
hash check still passes. A subsequent SMB2 CREATE of a child under
that parent drives smb2_open() into smb_inherit_dacl() (share has
"vfs objects = acl_xattr" set), which fails the page allocator:
WARNING: mm/page_alloc.c:5226 at __alloc_frozen_pages_noprof+0x46c/0x9c0
Workqueue: ksmbd-io handle_ksmbd_work
__alloc_frozen_pages_noprof+0x46c/0x9c0
___kmalloc_large_node+0x68/0x130
__kmalloc_large_node_noprof+0x24/0x70
__kmalloc_noprof+0x4c9/0x690
smb_inherit_dacl+0x394/0x2430
smb2_open+0x595d/0xabe0
handle_ksmbd_work+0x3d3/0x1140
With the patch applied the added guard rejects the tampered value
with -EINVAL before any large allocation runs, smb2_open() falls back
to smb2_create_sd_buffer(), and the child is created with a default
SD. No warning, no splat.
Fix by:
1. Validating num_aces against pdacl_size using the same formula
applied in parse_dacl().
2. Replacing the raw kmalloc(sizeof * num_aces * 2) with
kmalloc_array(num_aces * 2, sizeof(...)) for overflow-safe
allocation.
3. Tightening the per-ACE loop guard to require the minimum valid
ACE size (offsetof(smb_ace, sid) + CIFS_SID_BASE_SIZE) and
rejecting under-sized ACEs, matching the hardening in
smb_check_perm_dacl() and parse_dacl().
v1 -> v2:
- Replace the synthetic test-module splat in the changelog with a
real-path UML + KASAN reproduction driven through mount.cifs and
SMB2 CREATE; Namjae flagged the kcifs3_test_inherit_dacl_old name
in v1 since it does not exist in ksmbd.
- Drop the commit-hash citation from the code comment per Namjae's
review; keep the parse_dacl() pointer.
来源: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
来源: CVE Program / CVE List V5
Vulnerability Type
N/A
来源: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
来源: 中国国家信息安全漏洞库 CNNVD
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smb_inherit_dacl()未验证num_aces值，可能导致堆分配过大且未初始化，以及ACE遍历使用过小的最小大小检查。
来源: 中国国家信息安全漏洞库 CNNVD
CVSS Information
N/A
来源: 中国国家信息安全漏洞库 CNNVD
Vulnerability Type
N/A
来源: 中国国家信息安全漏洞库 CNNVD
受影响产品
二、漏洞 CVE-2026-31706 的公开POC
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CVE-2026-31706 补丁与修复 (4)
同批安全公告 · Linux · 2026-05-01 · 共 146 条
| CVE-2026-43037 | 9.8 CRITICAL | Linux kernel 缓冲区错误漏洞 |
| CVE-2026-43038 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-43039 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-43011 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-31705 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-31718 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-43048 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31739 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31735 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31773 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31717 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-43018 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31709 | 8.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31712 | 8.3 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31779 | 8.1 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31771 | 8.1 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31708 | 8.1 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-43051 | 8.1 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-43019 | 7.8 HIGH | Linux kernel 安全漏洞 |
| CVE-2026-31772 | 7.8 HIGH | Linux kernel 安全漏洞 |
显示前 20 条，共 146 条。 查看全部 → →
IV. Related Vulnerabilities
V. Comments for CVE-2026-31706
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