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CVE-2026-74521— ksmbd: use memcmp() to compare ClientGUIDs

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 5.15版本存在安全漏洞，该漏洞源于ksmbd使用strncmp()比较ClientGUID时，由于ClientGUID为固定大小的二进制值且可能包含嵌入的NUL字节，strncmp()会在第一个NUL字节处停止比较，导致不同的ClientGUID值可能被错误地视为相等。

CVSS 9.1 · Critical EPSS 0.41% · P33

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 7bde6f181fa307d2cc1ec2b0313ac8e9811c8232 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 5a0367bf5ce420be7b19936def2e90adcf32a683 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< ba2a5b66f1d414eb8403d655f8813783892cfc85 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< a386c83043015a703e227775f778e40343f45911 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< d535363299822c5caa543787b21bd5cfa3e41949 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< e8bb506e6ef749ac0336f3e579d8d02396b7d832 affected
5.15 affected
< 5.15 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-74521

Vulnerability Information
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Vulnerability Title
ksmbd: use memcmp() to compare ClientGUIDs
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: use memcmp() to compare ClientGUIDs ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal. Use memcmp() in SMB3 multichannel session binding and FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE bytes.
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:N
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 5.15版本存在安全漏洞，该漏洞源于ksmbd使用strncmp()比较ClientGUID时，由于ClientGUID为固定大小的二进制值且可能包含嵌入的NUL字节，strncmp()会在第一个NUL字节处停止比较，导致不同的ClientGUID值可能被错误地视为相等。
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 e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 ~ 7bde6f181fa307d2cc1ec2b0313ac8e9811c8232 -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-74521

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III. Intelligence Information for CVE-2026-74521

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Patches & Fixes for CVE-2026-74521 (4)

Other References for CVE-2026-74521 (2)

Same Patch Batch · Linux · 2026-08-15 · 844 CVEs total

CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72046 9.8 CRITICAL gve: fix header buffer corruption with header-split and HW-GRO
CVE-2026-74376 9.8 CRITICAL md/raid10: reset read_slot when reusing r10bio for discard
CVE-2026-72217 9.8 CRITICAL SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing
CVE-2026-74384 9.8 CRITICAL nvme-multipath: fix flex array size in struct nvme_ns_head
CVE-2026-72299 9.8 CRITICAL tipc: restrict socket queue dumps in enqueue tracepoints
CVE-2026-72210 9.8 CRITICAL ntfs: fix off-by-one in mapping pairs decoding bounds checks
CVE-2026-72211 9.8 CRITICAL ntfs: grow index root value before reparent header update
CVE-2026-72209 9.8 CRITICAL ntfs: validate attribute values on lookup
CVE-2026-72317 9.8 CRITICAL SUNRPC: pin upper rpc_clnt across the TLS connect_worker
CVE-2026-74267 9.8 CRITICAL net/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring q
CVE-2026-72206 9.8 CRITICAL ntfs: validate index block header more strictly
CVE-2026-72207 9.8 CRITICAL ntfs: not change 0-byte $DATA attribute to non-resident

Showing top 20 of 844 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74521

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