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CVE-2026-89640— cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

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cifs_remap_file_range()在len为0时有效长度计算发生loff_t下溢，可能导致FSCTL_DUPLICATE_EXTENTS_TO_FILE请求中的ByteCount被破坏及范围反转。

CVSS 7.1 · High EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1601 · Modify System Image

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 04b38d601239b4d9be641b412cf4b7456a041c67< f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4 affected
04b38d601239b4d9be641b412cf4b7456a041c67< 7f62817fe049b0f3652518c1ba72631ec1e0a322 affected
04b38d601239b4d9be641b412cf4b7456a041c67< b098f5e5858797827666e6cd73033f52fc39b5f6 affected
04b38d601239b4d9be641b412cf4b7456a041c67< c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028 affected
04b38d601239b4d9be641b412cf4b7456a041c67< b057ca17b656345d04669cb87f2aff9b31d873db affected
04b38d601239b4d9be641b412cf4b7456a041c67< 6c322f5cf7476ded7a9a20f7be72462065a03c68 affected
4.5 affected
< 4.5 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-89640

Vulnerability Information
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Vulnerability Title
cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于cifs_remap_file_range()在len为0时有效长度计算发生loff_t下溢，可能导致FSCTL_DUPLICATE_EXTENTS_TO_FILE请求中的ByteCount被破坏及范围反转。
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 04b38d601239b4d9be641b412cf4b7456a041c67 ~ f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4 -
Linux Linux 4.5 -

II. Public POCs for CVE-2026-89640

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III. Intelligence Information for CVE-2026-89640

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Patches & Fixes for CVE-2026-89640 (5)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89656 9.8 CRITICAL libceph: reject buckets with mismatched CRUSH ids
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89640

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