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CVE-2026-63828

Updated on 19 Jul 2026

Severity

8.4 High severity

Details

CVSS score
8.4
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Links
NISTCIRCLRHELUbuntu

Overview

About vulnerability

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.

Details

Affected product:
Debian 10 ELS , Debian 11 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
Affected packages:
linux @ 5.4.0 (+4 more)

Fixes

KernelCare state

Live-patch status from KernelCare for each operating system.

Operating system Status Covered kernels
Debian 11 In Rollout
44 kernels
  • 5.10.46-5
  • 5.10.70-1
  • 5.10.46-4
  • 5.10.84-1
  • 5.10.92-1
  • 5.10.92-2
  • 5.10.103-1
  • 5.10.106-1
  • 5.10.113-1
  • 5.10.120-1
  • 5.10.127-1
  • 5.10.127-2
  • 5.10.136-1
  • 5.10.140-1
  • 5.10.149-1
  • 5.10.149-2
  • 5.10.158-2
  • 5.10.162-1
  • 5.10.179-1
  • 5.10.179-2
  • 5.10.179-3
  • 5.10.179-5
  • 5.10.191-1
  • 5.10.197-1
  • 5.10.178-3
  • 5.10.205-2
  • 5.10.205-1
  • 5.10.209-2
  • 5.10.216-1
  • 5.10.218-1
  • 5.10.221-1
  • 5.10.223-1
  • 5.10.226-1
  • 5.10.234-1
  • 5.10.237-1
  • 5.10.244-1
  • 5.10.247-1
  • 5.10.249-1
  • 5.10.251-1
  • 5.10.251-3
  • 5.10.251-4
  • 5.10.251-5
  • 5.10.257-1
  • 5.10.259-1
Debian 11 cloud In Rollout
24 kernels
  • 5.10.113-1
  • 5.10.179-2
  • 5.10.179-3
  • 5.10.179-5
  • 5.10.191-1
  • 5.10.197-1
  • 5.10.205-2
  • 5.10.209-2
  • 5.10.216-1
  • 5.10.218-1
  • 5.10.221-1
  • 5.10.223-1
  • 5.10.226-1
  • 5.10.234-1
  • 5.10.237-1
  • 5.10.244-1
  • 5.10.247-1
  • 5.10.249-1
  • 5.10.251-1
  • 5.10.251-3
  • 5.10.251-4
  • 5.10.251-5
  • 5.10.257-1
  • 5.10.259-1
Debian 13 Planned —