CVE-2026-63828
AppArmor bypass: MSG_FASTOPEN lets confined tasks open blocked TCP/MPTCP connections.
Is CVE-2026-63828 being exploited?
Not confirmed. CVE-2026-63828 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.13% probability of exploitation in the next 30 days.
How severe is CVE-2026-63828?
CVE-2026-63828 is rated High. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-63828?
Yes. A fix has been recorded for CVE-2026-63828. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-63828 affect?
CVE-2026-63828 affects Linux kernel with AppArmor enabled, Distributions: Ubuntu, Debian, SUSE, openSUSE, others. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-63828?
Apply vendor/kernel AppArmor updates immediately; restrict MSG_FASTOPEN if possible.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Confined AppArmor processes can bypass connect mediation using MSG_FASTOPEN to open outbound TCP/MPTCP connections that connect(2) would block, enabling unauthorized network access.
Immediate action required
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < a16714e7cf2baa98ba2efddd5d6cbac641f4e76b
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 20383429b56974507c465d016e5238b189f7a246
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 7f57428ce00891d26b0f087ef754a4d820ec83aa
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < faea60deaa05c76f0772650f42eafde12bd39d93
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 07b71c342382b854ab8030b244aeab6a7228ad7d
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 4a69b83045d3195d5b9a9b053ad840ddb2998b4e
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 45ebb934ea50b436ce49b2f159f090dab0d7fa28
- affected>= cf60af03ca4e71134206809ea892e49b92a88896 and < 4d587cd8a72155089a627130bbd4716ec0856e21
- affected3.6
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.