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CVE-2026-68388— smb/client: handle overlapping allocated ranges in fallocate

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fallocate处理重叠分配范围时，服务器返回的分配范围起始于当前偏移量之前，导致跳过空洞未清零，后续写入可能失败，且畸形范围长度可能导致越界读取。

CVSS 9.8 · Critical EPSS 0.51% · P42

Affected Version Matrix 23

VendorProduct Version RangeStatus
Linux Linux c406bb9ece6ef63721daab106f132ff4b4234e81< aeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< 01719883235507b1585e4c51e320d9a7113dc698 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< f47c7277c03a636fcc3a57969f2dc09567b3c050 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< 437637f5ff3f573b2edf8571de91fb00a21eb4e6 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< 377fe3e583e46369ee1004d5cfe12271d6589a68 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< 7e08ab7a061b17ac1989a225c6afb53f44a86808 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< a4a09e5142835633fffbde68bd0a039ba4d4bf97 affected
966a3cb7c7db786452a87afdc3b48858fc4d4d6b< b09ae45d85dc816987a71db9eebc54b0ae288e94 affected
… +15 more rows
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I. Basic Information for CVE-2026-68388

Vulnerability Information
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Vulnerability Title
smb/client: handle overlapping allocated ranges in fallocate
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlapping allocated ranges in fallocate smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC. The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset. For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200): Request: [100, 400) Server range: [ 0, 200) allocated Correct: [100, 200) allocated data, skip [200, 400) hole, zero-fill Current: [100, 300) skipped [300, 400) zero-filled afterwards The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled. Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows. This also prevents a malformed range length from causing an out-of-bounds zero-buffer read.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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fallocate处理重叠分配范围时，服务器返回的分配范围起始于当前偏移量之前，导致跳过空洞未清零，后续写入可能失败，且畸形范围长度可能导致越界读取。
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 c406bb9ece6ef63721daab106f132ff4b4234e81 ~ aeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2 -
Linux Linux 5.14 -

II. Public POCs for CVE-2026-68388

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III. Intelligence Information for CVE-2026-68388

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Patches & Fixes for CVE-2026-68388 (8)

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

CVE-2026-68136 9.8 CRITICAL net: gro: fix double aggregation of flush-marked skbs
CVE-2026-68144 9.8 CRITICAL phonet: pep: fix use-after-free in pep_get_sb()
CVE-2026-68154 9.8 CRITICAL libceph: reject zero bucket types in crush_decode
CVE-2026-68156 9.8 CRITICAL libceph: refresh auth->authorizer_buf{,_len} after authorizer update
CVE-2026-68158 9.8 CRITICAL libceph: Fix multiplication overflow in decode_new_up_state_weight()
CVE-2026-68159 9.8 CRITICAL libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE
CVE-2026-68160 9.8 CRITICAL ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()
CVE-2026-68161 9.8 CRITICAL sctp: close UDP tunnel sockets during netns teardown
CVE-2026-68300 9.8 CRITICAL sctp: auth: verify auth requirement when auth_chunk is NULL
CVE-2026-68170 9.8 CRITICAL mptcp: fix stale skb->sk reference on subflow close
CVE-2026-68302 9.8 CRITICAL amt: re-read skb header pointers after every pull
CVE-2026-68137 9.8 CRITICAL net/x25: fix use-after-free in x25_kill_by_neigh()
CVE-2026-68123 9.8 CRITICAL openvswitch: fix GSO userspace truncation underflow
CVE-2026-68127 9.8 CRITICAL ila: reload IPv6 header after pskb_may_pull in checksum adjust
CVE-2026-68426 9.8 CRITICAL xfrm: fix stale skb->prev after async crypto steals a GSO segment
CVE-2026-68117 9.8 CRITICAL tipc: clear sock->sk on the failed-insert path in tipc_sk_create()
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-2026-68124 9.6 CRITICAL mctp: serial: handle zero-length frames to prevent rx buffer overflow
CVE-2026-68083 9.1 CRITICAL ksmbd: fix path resolution in ksmbd_vfs_kern_path_create

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-2026-68388

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