apparmor: mediate the implicit connect of TCP fast open sendmsg

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Summary

CVECVE-2026-63828
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 12:16:56 UTC
Updated2026-07-20 15:16:49 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 8.4 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

EPSS: 0.001690000 probability, percentile 0.066020000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.4HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
3.1CNADECLARED8.4HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 7f57428ce00891d26b0f087ef754a4d820ec83aa git Not specified
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 faea60deaa05c76f0772650f42eafde12bd39d93 git Not specified
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 07b71c342382b854ab8030b244aeab6a7228ad7d git Not specified
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 4a69b83045d3195d5b9a9b053ad840ddb2998b4e git Not specified
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 45ebb934ea50b436ce49b2f159f090dab0d7fa28 git Not specified
CNA Linux Linux affected cf60af03ca4e71134206809ea892e49b92a88896 4d587cd8a72155089a627130bbd4716ec0856e21 git Not specified
CNA Linux Linux affected 3.6 Not specified
CNA Linux Linux unaffected 3.6 semver Not specified
CNA Linux Linux unaffected 6.1.177 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.144 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.95 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.38 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.3 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7f57428ce00891d26b0f087ef754a4d820ec83aa 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/45ebb934ea50b436ce49b2f159f090dab0d7fa28 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4d587cd8a72155089a627130bbd4716ec0856e21 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/faea60deaa05c76f0772650f42eafde12bd39d93 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4a69b83045d3195d5b9a9b053ad840ddb2998b4e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/07b71c342382b854ab8030b244aeab6a7228ad7d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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