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CVE-2026-68166— userfaultfd: prevent registration of special VMAs

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存在安全漏洞，该漏洞源于userfaultfd允许注册特殊VMA，导致攻击者可丢弃页面并通过UFFDIO_COPY注入包含特定返回地址的页面，可能造成权限提升。

AI Predicted 4.7 Difficulty: Hard EPSS 0.20% · P10

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux 54007f818206dc27309ca423df4c87dd160a7208< d974b4b786214883bd8e56bda10b454c80fd6205 affected
54007f818206dc27309ca423df4c87dd160a7208< 495a28d5a100be1b232633f4c2dcc42ba10b3796 affected
54007f818206dc27309ca423df4c87dd160a7208< 165613191ad9d034bf17c00e3a142f9561597ec5 affected
54007f818206dc27309ca423df4c87dd160a7208< 0c26202b157f1efc3cd2f26f5c30f59b508a6a5d affected
54007f818206dc27309ca423df4c87dd160a7208< 3c58f641e813c3c71039f8fd4d4e2a3aab713288 affected
6.6 affected
< 6.6 unaffected
6.6.153≤ 6.6.* unaffected
… +4 more rows
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I. Basic Information for CVE-2026-68166

Vulnerability Information
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Vulnerability Title
userfaultfd: prevent registration of special VMAs
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: userfaultfd: prevent registration of special VMAs Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL.
Source: CVE Program / CVE List V5
CVSS Information
N/A
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存在安全漏洞，该漏洞源于userfaultfd允许注册特殊VMA，导致攻击者可丢弃页面并通过UFFDIO_COPY注入包含特定返回地址的页面，可能造成权限提升。
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 54007f818206dc27309ca423df4c87dd160a7208 ~ d974b4b786214883bd8e56bda10b454c80fd6205 -
Linux Linux 6.6 -

II. Public POCs for CVE-2026-68166

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III. Intelligence Information for CVE-2026-68166

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Patches & Fixes for CVE-2026-68166 (5)

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

CVE-2026-68159 9.8 CRITICAL libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE
CVE-2026-68381 9.8 CRITICAL ksmbd: pin conn during async oplock break notification
CVE-2026-68385 9.8 CRITICAL s390/checksum: Fix csum_partial() without vector facility
CVE-2026-68388 9.8 CRITICAL smb/client: handle overlapping allocated ranges in fallocate
CVE-2026-68117 9.8 CRITICAL tipc: clear sock->sk on the failed-insert path in tipc_sk_create()
CVE-2026-68170 9.8 CRITICAL mptcp: fix stale skb->sk reference on subflow close
CVE-2026-68161 9.8 CRITICAL sctp: close UDP tunnel sockets during netns teardown
CVE-2026-68123 9.8 CRITICAL openvswitch: fix GSO userspace truncation underflow
CVE-2026-68160 9.8 CRITICAL ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()
CVE-2026-68127 9.8 CRITICAL ila: reload IPv6 header after pskb_may_pull in checksum adjust
CVE-2026-68144 9.8 CRITICAL phonet: pep: fix use-after-free in pep_get_sb()
CVE-2026-68137 9.8 CRITICAL net/x25: fix use-after-free in x25_kill_by_neigh()
CVE-2026-68302 9.8 CRITICAL amt: re-read skb header pointers after every pull
CVE-2026-68300 9.8 CRITICAL sctp: auth: verify auth requirement when auth_chunk is NULL
CVE-2026-68426 9.8 CRITICAL xfrm: fix stale skb->prev after async crypto steals a GSO segment
CVE-2026-68136 9.8 CRITICAL net: gro: fix double aggregation of flush-marked skbs
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-2026-68156 9.8 CRITICAL libceph: refresh auth->authorizer_buf{,_len} after authorizer update
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-2026-68166

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