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CVE-2026-63828

8.4 · HIGH

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 connec…

Published Jul 19, 2026EPSS 0.17%

Overview

CVE-2026-63828 is a high-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 8.4 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.4, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/07b71c342382b854ab8030b244aeab6a7228ad7dRefgit.kernel.org/stable/c/20383429b56974507c465d016e5238b189f7a246Refgit.kernel.org/stable/c/45ebb934ea50b436ce49b2f159f090dab0d7fa28Refgit.kernel.org/stable/c/4a69b83045d3195d5b9a9b053ad840ddb2998b4eRefgit.kernel.org/stable/c/4d587cd8a72155089a627130bbd4716ec0856e21Refgit.kernel.org/stable/c/7f57428ce00891d26b0f087ef754a4d820ec83aaRefgit.kernel.org/stable/c/a16714e7cf2baa98ba2efddd5d6cbac641f4e76bRefgit.kernel.org/stable/c/faea60deaa05c76f0772650f42eafde12bd39d93

How CyberStrike helps

Frequently asked questions

What is CVE-2026-63828?

CVE-2026-63828 is a high-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 8.4 (HIGH).

How severe is CVE-2026-63828?

This vulnerability has a CVSS 3.1 base score of 8.4, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-63828?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-63828?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-63828 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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