In the Linux kernel, the following vulnerability has been resolved: apparmor: mediate the implicit connect of TCP fast open sendmsg… (CVE-2026-63828)
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.
In the Linux kernel, the following vulnerability has been resolved: apparmor: mediate the implicit connect of TCP fast open sendmsg… (CVE-2026-63828)
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.
CVSS v3.1
Score 8.4high
Affected software
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-fvhv-v8p3-vrwq
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-63828"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a5d27ad2a4a8d598913125d
Added to database: 07/19/2026, 19:38:21 UTC
Last enriched: 08/15/2026, 03:28:49 UTC
Last updated: 08/28/2026, 22:52:12 UTC
Views: 61
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