CVE-2026-63828

apparmor: mediate the implicit connect of TCP fast open sendmsg

HIGH

8.4

CVSS Score

Published: July 19, 2026 at 12:02 PM UTC

Updated: August 17, 2026 at 05:17 AM UTC

1 product affected across 1 vendorLinux Kernel

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Severity

HIGH8.4

Exploit prediction

EPSS 0.2%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel · Linux

95%

3.6 ≤ v < 5.10.2613.6 ≤ v < 5.15.2123.6 ≤ v < 6.1.1773.6 ≤ v < 6.12.953.6 ≤ v < 6.18.383.6 ≤ v < 6.6.1443.6 ≤ v < 7.1.33.6 ≤ v < 7.23.6cf60af03ca4e71134206809ea892e49b92a88896

Vendor states this is fixed in 07b71c342382b854ab8030b244aeab6a7228ad7d (fixed)

Vendor states this is fixed in 20383429b56974507c465d016e5238b189f7a246 (fixed)

Vendor states this is fixed in 45ebb934ea50b436ce49b2f159f090dab0d7fa28 (fixed)

Vendor states this is fixed in 4a69b83045d3195d5b9a9b053ad840ddb2998b4e (fixed)

Vendor states this is fixed in 4d587cd8a72155089a627130bbd4716ec0856e21 (fixed)

Vendor states this is fixed in 7f57428ce00891d26b0f087ef754a4d820ec83aa (fixed)

Vendor states this is fixed in a16714e7cf2baa98ba2efddd5d6cbac641f4e76b (fixed)

Vendor states this is fixed in faea60deaa05c76f0772650f42eafde12bd39d93 (fixed)

Vendor states this is fixed in 3.6 (unaffected)

Vendor states this is fixed in 5.10.261 (unaffected)

Vendor states this is fixed in 5.15.212 (unaffected)

Vendor states this is fixed in 6.1.177 (unaffected)