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CVE-2026-64514— userfaultfd: gate must_wait writability check on pte_present()

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基金会开源的一款操作系统内核。 Linux kernel 4.11版本存在安全漏洞，该漏洞源于在检查userfaultfd可写性时未正确检查PTE存在性，可能导致未经定义的结果或线程挂起。

AI Predicted 3.3 Difficulty: Hard EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 369cd2121be440543280b91056de187f625d0dbb< a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f affected
369cd2121be440543280b91056de187f625d0dbb< d4026417e8184d13850a0bad4d96ceb6ed9f7152 affected
369cd2121be440543280b91056de187f625d0dbb< 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0 affected
369cd2121be440543280b91056de187f625d0dbb< 5f4dbdb0a87596214076b20b94f2b71b522170b3 affected
369cd2121be440543280b91056de187f625d0dbb< a6e9a4939e359599701b1da351e84f72e021443a affected
369cd2121be440543280b91056de187f625d0dbb< 60d696a037eeeedfb57756dfe7ec08a1587c8631 affected
369cd2121be440543280b91056de187f625d0dbb< 710183888174639a15fcec16cd1af766b8480bb7 affected
369cd2121be440543280b91056de187f625d0dbb< 8e80af52db652fbc41320eee45a4f73bc029faf2 affected
… +10 more rows
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I. Basic Information for CVE-2026-64514

Vulnerability Information
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Vulnerability Title
userfaultfd: gate must_wait writability check on pte_present()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: userfaultfd: gate must_wait writability check on pte_present() userfaultfd_must_wait() and userfaultfd_huge_must_wait() read the PTE without taking the page table lock and then apply pte_write() / huge_pte_write() to it. Those accessors decode bits from the present encoding only; on a swap or migration entry they read the offset bits that happen to share the same position and return an undefined result. The intent of the check is "is this fault still WP-blocked?". A non-marker swap entry means the page is in transit -- the userfault context the original fault delivered against is no longer the same, and the swap-in or migration completion path will re-deliver a fresh fault if userspace still needs to handle it. Worst case under the current code the garbage write bit says "wait", and the thread stays asleep until a UFFDIO_WAKE that may never arrive. Gate the writability check on pte_present() so the lockless re-check only inspects present-PTE bits when the entry is actually present. The non-present, non-marker case returns "don't wait" and lets the fault path retry.
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基金会开源的一款操作系统内核。 Linux kernel 4.11版本存在安全漏洞，该漏洞源于在检查userfaultfd可写性时未正确检查PTE存在性，可能导致未经定义的结果或线程挂起。
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 369cd2121be440543280b91056de187f625d0dbb ~ a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f -
Linux Linux 4.11 -

II. Public POCs for CVE-2026-64514

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III. Intelligence Information for CVE-2026-64514

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Patches & Fixes for CVE-2026-64514 (8)

Same Patch Batch · Linux · 2026-07-25 · 274 CVEs total

CVE-2026-64391 9.8 CRITICAL ksmbd: use opener credentials for ADS I/O
CVE-2026-64268 9.8 CRITICAL RDMA/siw: bound Read Response placement to the RREAD length
CVE-2026-64384 9.8 CRITICAL smb: client: fix change notify replay double-free
CVE-2026-64383 9.8 CRITICAL smb: client: fix double-free in SMB2_flush() replay
CVE-2026-64385 9.8 CRITICAL smb: client: fix double-free in SMB2_ioctl() replay
CVE-2026-64386 9.8 CRITICAL smb: client: fix query_info() replay double-free
CVE-2026-64387 9.8 CRITICAL smb: client: fix query directory replay double-free
CVE-2026-64439 9.8 CRITICAL crypto: krb5 - filter out async aead implementations at alloc
CVE-2026-64303 9.8 CRITICAL spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
CVE-2026-64355 9.8 CRITICAL bpf: Reject fragmented frames in devmap
CVE-2026-64459 9.8 CRITICAL tcp: restore RCU grace period in tcp_ao_destroy_sock
CVE-2026-64399 9.8 CRITICAL ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE
CVE-2026-64410 9.8 CRITICAL netfilter: flowtable: IPIP tunnel hardware offload is not yet support
CVE-2026-64397 9.8 CRITICAL ksmbd: serialize QUERY_DIRECTORY requests per file
CVE-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64320 9.1 CRITICAL nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page
CVE-2026-64392 9.1 CRITICAL ksmbd: use opener credentials for delete-on-close
CVE-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
CVE-2026-64319 9.1 CRITICAL nvmet-auth: validate reply message payload bounds against transfer length

Showing top 20 of 274 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-64514

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