{"id":"CVE-2026-63828","title":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: mediate the implicit connect of TCP fast open sendmsg\n\nsendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and\nwrite(2): it opens the connecti…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: mediate the implicit connect of TCP fast open sendmsg\n\nsendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and\nwrite(2): it opens the connecti…","severity":"high","cvss":8.4,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N","published":"2026-07-19","updated":"2026-08-17","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-63828","references":[{"url":"https://git.kernel.org/stable/c/07b71c342382b854ab8030b244aeab6a7228ad7d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/20383429b56974507c465d016e5238b189f7a246","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/45ebb934ea50b436ce49b2f159f090dab0d7fa28","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4a69b83045d3195d5b9a9b053ad840ddb2998b4e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4d587cd8a72155089a627130bbd4716ec0856e21","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7f57428ce00891d26b0f087ef754a4d820ec83aa","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a16714e7cf2baa98ba2efddd5d6cbac641f4e76b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/faea60deaa05c76f0772650f42eafde12bd39d93","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","exploit-available"],"epss":0.0017,"epssPercentile":0.05655,"ingestedAt":"2026-08-17T05:47:50.025Z","exploits":{"github":1,"githubRepos":["https://github.com/4n4s4zi/tfo-connect-bypass"],"checkedAt":"2026-09-27T10:33:55.399Z"},"exploitAvailable":true,"slug":"CVE-2026-63828","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\napparmor: mediate the implicit connect of TCP fast open sendmsg\n\nsendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and\nwrite(2): it opens the connection in the SYN. apparmor_socket_sendmsg()\nonly checks AA_MAY_SEND, so a profile that grants send but denies connect\nlets a confined task open an outbound TCP/MPTCP connection that connect(2)\nwould have refused, bypassing connect mediation.\n\nMediate the implicit connect when MSG_FASTOPEN is set and a destination\nis supplied. Add it to apparmor_socket_sendmsg() (not the shared\naa_sock_msg_perm() helper, which recvmsg also uses) and call aa_sk_perm()\ndirectly, mirroring the selinux and tomoyo fixes. sk_is_tcp() does not\ncover MPTCP fast open, so the SOCK_STREAM/IPPROTO_MPTCP arm is explicit.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":58,"depthScoreParts":{"impact":46.2,"likelihood":0,"exploitation":12,"ransomware":0},"changes":[{"seq":5395,"id":"CVE-2026-63828","ts":1788887279182,"field":"exploit_available","old":"false","new":"true"},{"seq":4278,"id":"CVE-2026-63828","ts":1788886393225,"field":"exploit_available","old":"true","new":"false"},{"seq":3027,"id":"CVE-2026-63828","ts":1788883056826,"field":"exploit_available","old":"false","new":"true"},{"seq":2056,"id":"CVE-2026-63828","ts":1788882461341,"field":"exploit_available","old":"true","new":"false"},{"seq":1129,"id":"CVE-2026-63828","ts":1788881898410,"field":"exploit_available","old":"false","new":"true"}]}