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CVE-2026-64327— usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks

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 6.9版本存在安全漏洞，该漏洞源于usb gadget f_fs模块中epfile->in初始化时机过晚，导致在USB主机连接之前用户空间ioctl执行时端点方向检查错误，从而产生错误的DMA方向。

AI Predicted 6.5 Difficulty: Easy EPSS 0.16% · P5

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 7b07a2a7ca02a20124b552be96c5a56910795488< 82cf1142e5ccf2b6d6d22ef713aaf3e5f2b5716b affected
7b07a2a7ca02a20124b552be96c5a56910795488< 9e04055ab5fc0470a0031ee6934739f9aa8f34a5 affected
7b07a2a7ca02a20124b552be96c5a56910795488< f99f32ea9aa976afcbec20647ed33b50a52002c1 affected
7b07a2a7ca02a20124b552be96c5a56910795488< 82cfd4739011bdc7e87b5d585703427e89ddfaa5 affected
6.9 affected
< 6.9 unaffected
6.12.96≤ 6.12.* unaffected
6.18.39≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-64327

Vulnerability Information
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Vulnerability Title
usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks When parsing endpoint descriptors, ffs_data_got_descs() generates the eps_addrmap which contains the endpoint direction. However, epfile->in was previously only populated in ffs_func_eps_enable() which executes upon USB host connection. As a result, early userspace ioctls like FUNCTIONFS_DMABUF_ATTACH that run before the host connects would see epfile->in as 0, leading to incorrect DMA directions. By moving the initialization to ffs_epfiles_create(), epfile->in is accurate before userspace opens the endpoint files.
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 6.9版本存在安全漏洞，该漏洞源于usb gadget f_fs模块中epfile->in初始化时机过晚，导致在USB主机连接之前用户空间ioctl执行时端点方向检查错误，从而产生错误的DMA方向。
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 7b07a2a7ca02a20124b552be96c5a56910795488 ~ 82cf1142e5ccf2b6d6d22ef713aaf3e5f2b5716b -
Linux Linux 6.9 -

II. Public POCs for CVE-2026-64327

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III. Intelligence Information for CVE-2026-64327

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Patches & Fixes for CVE-2026-64327 (4)

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-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
CVE-2026-64257 9.1 CRITICAL smb: client: reject overlapping data areas in SMB2 responses
CVE-2026-64319 9.1 CRITICAL nvmet-auth: validate reply message payload bounds against transfer length
CVE-2026-64320 9.1 CRITICAL nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials

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-2026-64327

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