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CVE-2026-64422— net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

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 2.6.24版本存在安全漏洞，该漏洞源于TCP reordering sysctl写入未正确验证，负数写入后造成整数溢出，导致MTU探测路径中的越界读取。

CVSS 7.1 · High EPSS 0.14% · P3

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< f0d88a4cd03affff6c08adf6c63964e235aede43 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< 27ddf4486c7dbf5bdd393fa8bef6b67179796d98 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< 782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< e81f805824a8109504fce090641b17d135b48cd1 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< 99206ce2244f8a3ed64298d0667c9055845a5dc7 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< bbae351c0f32f7c200249e4aa6561b2b419dcf69 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< a094ac95d3b69adfa1676eb9c8eae6835d4f1671 affected
91cc17c0e5e5ada156a8d5787a2509d263ea6bbf< efb8763d7bbb40cff4cc55a6b62c3095a038149c affected
… +10 more rows
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I. Basic Information for CVE-2026-64422

Vulnerability Information
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Vulnerability Title
net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP socket state. The sysctl is stored as an `int` but copied into the `u32` `tp->reordering` field for new sockets, so negative writes wrap to large values. With `tcp_mtu_probing=2`, the wrapped value can overflow the `tcp_mtu_probe()` size calculation and drive the MTU probing path into an out-of-bounds read. Route `tcp_reordering` writes through `proc_dointvec_minmax()` and require it to be at least 1. Also require `tcp_max_reordering` to be at least 1 so the configured maximum cannot become negative either. When registering the table for a non-init network namespace, relocate `extra2` pointers that refer into `init_net.ipv4` so the `tcp_reordering` upper bound follows that namespace's `tcp_max_reordering`. Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`. This keeps the send queue and window checks from being bypassed through signed integer overflow.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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 2.6.24版本存在安全漏洞，该漏洞源于TCP reordering sysctl写入未正确验证，负数写入后造成整数溢出，导致MTU探测路径中的越界读取。
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 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf ~ f0d88a4cd03affff6c08adf6c63964e235aede43 -
Linux Linux 2.6.24 -

II. Public POCs for CVE-2026-64422

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III. Intelligence Information for CVE-2026-64422

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Patches & Fixes for CVE-2026-64422 (8)

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-2026-64422

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