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CVE-2026-63867— mptcp: close TOCTOU race while computing rcv_wnd

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 5.11版本存在安全漏洞，该漏洞源于MPTCP输出路径在计算接收窗口时存在TOCTOU竞争条件，可能导致数据不一致，从而可能混淆对端。

CVSS 8.2 · High EPSS 0.59% · P46

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux fa3fe2b150316b294f2c662653501273ff25bba8< 301a33fd590c408a05c5df800e0cc1e6a8a2f8f8 affected
fa3fe2b150316b294f2c662653501273ff25bba8< 68364963e5baf03f16b4420292291f75c8f66497 affected
fa3fe2b150316b294f2c662653501273ff25bba8< 907ac6b1658e0277f979fcdfae2a753b495c1510 affected
fa3fe2b150316b294f2c662653501273ff25bba8< c4f4cf60797974873dbc8e100144682a6f2f861f affected
fa3fe2b150316b294f2c662653501273ff25bba8< 3b8cbba7c0ed31189c89f90be247b8973ffa79ef affected
fa3fe2b150316b294f2c662653501273ff25bba8< 8f4f0a157e8436a05bf8c3670b24dbc258911c43 affected
fa3fe2b150316b294f2c662653501273ff25bba8< 8ab24fdebc369c0dfb90f82c1650b1e66662bb45 affected
5.11 affected
… +8 more rows
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I. Basic Information for CVE-2026-63867

Vulnerability Information
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Vulnerability Title
mptcp: close TOCTOU race while computing rcv_wnd
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: mptcp: close TOCTOU race while computing rcv_wnd The MPTCP output path access locklessly the MPTCP-level ack_seq in multiple times, using possibly different values for the data_ack in the DSS option and to compute the announced rcv wnd for the same packet. Refactor the cote to avoid inconsistencies which may confuse the peer. Also ensure that the MPTCP level rcv wnd is updated only when the egress packet actually contains a DSS ack.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 5.11版本存在安全漏洞，该漏洞源于MPTCP输出路径在计算接收窗口时存在TOCTOU竞争条件，可能导致数据不一致，从而可能混淆对端。
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 fa3fe2b150316b294f2c662653501273ff25bba8 ~ 301a33fd590c408a05c5df800e0cc1e6a8a2f8f8 -
Linux Linux 5.11 -

II. Public POCs for CVE-2026-63867

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III. Intelligence Information for CVE-2026-63867

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Patches & Fixes for CVE-2026-63867 (6)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64089 9.8 CRITICAL batman-adv: tt: fix negative last_changeset_len
CVE-2026-53398 9.8 CRITICAL NFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-63978 9.8 CRITICAL net/handshake: Drain pending requests at net namespace exit
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-63886 9.8 CRITICAL scsi: target: iscsi: Validate CHAP_R length before base64 decode
CVE-2026-64162 9.8 CRITICAL idpf: fix read_dev_clk_lock spinlock init in idpf_ptp_init()
CVE-2026-64035 9.8 CRITICAL igc: set tx buffer type for SMD frames
CVE-2026-64150 9.8 CRITICAL netfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-63922 9.8 CRITICAL ipv6: exthdrs: refresh nh after handling HAO option

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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