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CVE-2026-63828— apparmor: mediate the implicit connect of TCP fast open sendmsg

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 3.6版本存在安全漏洞，该漏洞源于AppArmor对TCP fast open的sendmsg隐式连接缺乏访问控制，可能导致绕过连接检查并进行未授权的远程TCP连接。

CVSS 8.4 · High EPSS 0.13% · P3

Possible ATT&CK Techniques 1 AI

T1041 · Exfiltration Over C2 Channel

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux cf60af03ca4e71134206809ea892e49b92a88896< a16714e7cf2baa98ba2efddd5d6cbac641f4e76b affected
cf60af03ca4e71134206809ea892e49b92a88896< 20383429b56974507c465d016e5238b189f7a246 affected
cf60af03ca4e71134206809ea892e49b92a88896< 7f57428ce00891d26b0f087ef754a4d820ec83aa affected
cf60af03ca4e71134206809ea892e49b92a88896< faea60deaa05c76f0772650f42eafde12bd39d93 affected
cf60af03ca4e71134206809ea892e49b92a88896< 07b71c342382b854ab8030b244aeab6a7228ad7d affected
cf60af03ca4e71134206809ea892e49b92a88896< 4a69b83045d3195d5b9a9b053ad840ddb2998b4e affected
cf60af03ca4e71134206809ea892e49b92a88896< 45ebb934ea50b436ce49b2f159f090dab0d7fa28 affected
cf60af03ca4e71134206809ea892e49b92a88896< 4d587cd8a72155089a627130bbd4716ec0856e21 affected
… +10 more rows
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I. Basic Information for CVE-2026-63828

Vulnerability Information
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Vulnerability Title
apparmor: mediate the implicit connect of TCP fast open sendmsg
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: apparmor: mediate the implicit connect of TCP fast open sendmsg sendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and write(2): it opens the connection in the SYN. apparmor_socket_sendmsg() only checks AA_MAY_SEND, so a profile that grants send but denies connect lets a confined task open an outbound TCP/MPTCP connection that connect(2) would have refused, bypassing connect mediation. Mediate the implicit connect when MSG_FASTOPEN is set and a destination is supplied. Add it to apparmor_socket_sendmsg() (not the shared aa_sock_msg_perm() helper, which recvmsg also uses) and call aa_sk_perm() directly, mirroring the selinux and tomoyo fixes. sk_is_tcp() does not cover MPTCP fast open, so the SOCK_STREAM/IPPROTO_MPTCP arm is explicit.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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基金会开源的一款操作系统内核。 Linux kernel 3.6版本存在安全漏洞，该漏洞源于AppArmor对TCP fast open的sendmsg隐式连接缺乏访问控制，可能导致绕过连接检查并进行未授权的远程TCP连接。
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 cf60af03ca4e71134206809ea892e49b92a88896 ~ a16714e7cf2baa98ba2efddd5d6cbac641f4e76b -
Linux Linux 3.6 -

II. Public POCs for CVE-2026-63828

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III. Intelligence Information for CVE-2026-63828

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Patches & Fixes for CVE-2026-63828 (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-2026-64160 9.8 CRITICAL netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
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-2026-64162 9.8 CRITICAL idpf: fix read_dev_clk_lock spinlock init in idpf_ptp_init()

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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