CVE-2026-63828

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < 7f57428ce00891d26b0f087ef754a4d820ec83aaaffected
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < faea60deaa05c76f0772650f42eafde12bd39d93affected
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < 07b71c342382b854ab8030b244aeab6a7228ad7daffected
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < 4a69b83045d3195d5b9a9b053ad840ddb2998b4eaffected
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < 45ebb934ea50b436ce49b2f159f090dab0d7fa28affected
LinuxLinuxcf60af03ca4e71134206809ea892e49b92a88896 < 4d587cd8a72155089a627130bbd4716ec0856e21affected
LinuxLinux3.6affected
LinuxLinux0 < 3.6unaffected
LinuxLinux6.1.177 <= 6.1.*unaffected
LinuxLinux6.6.144 <= 6.6.*unaffected
LinuxLinux6.12.95 <= 6.12.*unaffected
LinuxLinux6.18.38 <= 6.18.*unaffected
LinuxLinux7.1.3 <= 7.1.*unaffected
LinuxLinux7.2-rc1 <= *unaffected

Weaknesses

References