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CVE-2026-64380— smb: client: harden POSIX SID length parsing

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 5.7版本存在安全漏洞，该漏洞源于posix_info_sid_size()函数读取sid[1]以获取子权威计数时边界检查不足，仅要求剩余一个字节，实际需要两个字节，可能导致接受截断的POSIX SID，增加安全风险。

CVSS 8.2 · High EPSS 0.44% · P37

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 349e13ad30b45998bb9937cfe0b32be6f951976d< 171605aed68380c2fa75dff9b3a1ed427c50065b affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 4213c1208978483021d7d125c131de3985d38f61 affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 96e889bc1e759c83f25093e8c2f3da31b4973f30 affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 0de5b8e76847f5de26f364a82c6602c4881c30da affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 427eb7eb46425fec845a43e861f3d6e2899cae59 affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 86c5d470f5d42e61123b2f4b4f0b91f4eee5b980 affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 46a84715a015cb48e1b9c219dc88c03d8a541ea4 affected
349e13ad30b45998bb9937cfe0b32be6f951976d< 7ad2bcf2441430bb2e918fb3ef9a90d775a6e422 affected
… +10 more rows
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I. Basic Information for CVE-2026-64380

Vulnerability Information
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Vulnerability Title
smb: client: harden POSIX SID length parsing
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: harden POSIX SID length parsing posix_info_sid_size() reads sid[1] to obtain the subauthority count, but its existing boundary check still accepts buffers with only one remaining byte. Require two bytes before reading sid[1] so all client paths that reuse the helper reject truncated POSIX SIDs safely.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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基金会开源的一款操作系统内核。 Linux kernel 5.7版本存在安全漏洞，该漏洞源于posix_info_sid_size()函数读取sid[1]以获取子权威计数时边界检查不足，仅要求剩余一个字节，实际需要两个字节，可能导致接受截断的POSIX SID，增加安全风险。
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 349e13ad30b45998bb9937cfe0b32be6f951976d ~ 171605aed68380c2fa75dff9b3a1ed427c50065b -
Linux Linux 5.7 -

II. Public POCs for CVE-2026-64380

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III. Intelligence Information for CVE-2026-64380

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Patches & Fixes for CVE-2026-64380 (7)

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

CVE-2026-64355 9.8 CRITICAL bpf: Reject fragmented frames in devmap
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-2026-64268 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-2026-64439 9.8 CRITICAL crypto: krb5 - filter out async aead implementations at alloc
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-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64319 9.1 CRITICAL nvmet-auth: validate reply message payload bounds against transfer length
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
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-2026-64450 9.1 CRITICAL tipc: fix out-of-bounds read in broadcast Gap ACK blocks

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-2026-64380

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