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CVE-2026-63828

HIGHCVSS 8.4/10EPSS 0.13%

Last modified

CVE-2026-63828 is a high-severity vulnerability rated 8.4/10 on the CVSS scale. 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. EPSS estimates a 0.13% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
8.4/10

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

EPSS Probability
0.13%

3.1th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= cf60af03ca4e71134206809ea892e49b92a88896, < a16714e7cf2baa98ba2efddd5d6cbac641f4e76b; >= cf60af03ca4e71134206809ea892e49b92a88896, < 20383429b56974507c465d016e5238b189f7a246; >= cf60af03ca4e71134206809ea892e49b92a88896, < 7f57428ce00891d26b0f087ef754a4d820ec83aa; >= cf60af03ca4e71134206809ea892e49b92a88896, < faea60deaa05c76f0772650f42eafde12bd39d93; >= cf60af03ca4e71134206809ea892e49b92a88896, < 07b71c342382b854ab8030b244aeab6a7228ad7d; >= cf60af03ca4e71134206809ea892e49b92a88896, < 4a69b83045d3195d5b9a9b053ad840ddb2998b4e; >= cf60af03ca4e71134206809ea892e49b92a88896, < 45ebb934ea50b436ce49b2f159f090dab0d7fa28; >= cf60af03ca4e71134206809ea892e49b92a88896, < 4d587cd8a72155089a627130bbd4716ec0856e21
LinuxLinux3.6

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is 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.
How severe is CVE-2026-63828?
CVE-2026-63828 has a CVSS score of 8.4/10 (HIGH severity). The EPSS model estimates a 0.13% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63828?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST