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CVE-2026-64294— mm: do file ownership checks with the proper mount idmap

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存在安全漏洞，该漏洞源于在mincore()和madvise(MADV_PAGEOUT)中使用了错误的挂载idmap进行inode所有权检查，导致侧信道保护检查不正确，可能造成owner_or_capable()检查失败。

AI Predicted 3.7 Difficulty: Theoretical EPSS 0.16% · P5

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 9caccd41541a6f7d6279928d9f971f6642c361af< 7368bec565bac3e536cd43579dbde1e715e6ba61 affected
9caccd41541a6f7d6279928d9f971f6642c361af< b2f3d94ea310bea9d36d53e9d9b3f45e86c1d893 affected
9caccd41541a6f7d6279928d9f971f6642c361af< 744b23aa430d52f5c8e4dbff7d71496d6643bed2 affected
9caccd41541a6f7d6279928d9f971f6642c361af< 8344bdf0629457e532797b42d9d2bbf2a2900bbf affected
9caccd41541a6f7d6279928d9f971f6642c361af< 5c942ad7df75925ee166e7f0fb36892d8dde376b affected
9caccd41541a6f7d6279928d9f971f6642c361af< 04ba248d02d9eaa3d9077b00a6134caa75fa3e90 affected
9caccd41541a6f7d6279928d9f971f6642c361af< e187bc02f8fa4226d62814592cf064ee4557c470 affected
5.12 affected
… +8 more rows
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I. Basic Information for CVE-2026-64294

Vulnerability Information
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Vulnerability Title
mm: do file ownership checks with the proper mount idmap
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: mm: do file ownership checks with the proper mount idmap Ever since idmapped mounts were introduced, inode ownership checks (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done against the nop_mnt_idmap, which completely ignores the file's mount's idmap. This results in odd edgecases like: 1) mount/bind-mount with an idmap userA:userB:1 2) userB runs an owner_or_capable() check on file that is owned by userA on-disk/in-memory, but owned by userB after idmap translation 3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper idmap internally, but it does not need to be the case on e.g a 0444 file where even the owner itself doesn't have permissions to write to it. Since this is clearly not trivial to get right, introduce a file_owner_or_capable() that can carry the correct semantics, and switch the various users in mm to it. The issue was found by manual code inspection & an off-list discussion with Jan Kara.
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存在安全漏洞，该漏洞源于在mincore()和madvise(MADV_PAGEOUT)中使用了错误的挂载idmap进行inode所有权检查，导致侧信道保护检查不正确，可能造成owner_or_capable()检查失败。
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 9caccd41541a6f7d6279928d9f971f6642c361af ~ 7368bec565bac3e536cd43579dbde1e715e6ba61 -
Linux Linux 5.12 -

II. Public POCs for CVE-2026-64294

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III. Intelligence Information for CVE-2026-64294

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Patches & Fixes for CVE-2026-64294 (6)

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

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-2026-64303 9.8 CRITICAL spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
CVE-2026-64439 9.8 CRITICAL crypto: krb5 - filter out async aead implementations at alloc
CVE-2026-64410 9.8 CRITICAL netfilter: flowtable: IPIP tunnel hardware offload is not yet support
CVE-2026-64399 9.8 CRITICAL ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE
CVE-2026-64397 9.8 CRITICAL ksmbd: serialize QUERY_DIRECTORY requests per file
CVE-2026-64391 9.8 CRITICAL ksmbd: use opener credentials for ADS I/O
CVE-2026-64387 9.8 CRITICAL smb: client: fix query directory replay double-free
CVE-2026-64386 9.8 CRITICAL smb: client: fix query_info() replay double-free
CVE-2026-64385 9.8 CRITICAL smb: client: fix double-free in SMB2_ioctl() replay
CVE-2026-64383 9.8 CRITICAL smb: client: fix double-free in SMB2_flush() replay
CVE-2026-64384 9.8 CRITICAL smb: client: fix change notify replay double-free
CVE-2026-64268 9.8 CRITICAL RDMA/siw: bound Read Response placement to the RREAD length
CVE-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64257 9.1 CRITICAL smb: client: reject overlapping data areas in SMB2 responses
CVE-2026-64392 9.1 CRITICAL ksmbd: use opener credentials for delete-on-close
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
CVE-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
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-2026-64294

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