Affects the Linux kernel, a core widely deployed component; allows memory corruption with potential RCE/DoS across many systems and distributions.
CVE-2026-63978
Linux kernel net/handshake bug causes memory corruption, possible remote code execution.
Is CVE-2026-63978 being exploited?
Not confirmed. CVE-2026-63978 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 0.62% probability of exploitation in the next 30 days.
How severe is CVE-2026-63978?
CVE-2026-63978 is rated Critical with a CVSS score of 9.8. 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-2026-63978?
Yes. A fix has been recorded for CVE-2026-63978. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-63978 affect?
CVE-2026-63978 affects Linux kernel (net/handshake), Linux distributions with affected kernels, Containers/VMs using affected kernels. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-63978?
Apply vendor kernel patches and reboot affected hosts immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attackers can trigger list-corruption and use-after-free via handshake requests, enabling DoS or potential remote code execution.
Immediate action required
- affected>= 3b3009ea8abb713b022d94fba95ec270cf6e7eae and < 9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd
- affected>= 3b3009ea8abb713b022d94fba95ec270cf6e7eae and < 2bf24a7e190aae0ea47c78099938ae056c622e44
- affected>= 3b3009ea8abb713b022d94fba95ec270cf6e7eae and < 8c35539db0ab0bfa1ea44efab00b053261a69469
- affected>= 3b3009ea8abb713b022d94fba95ec270cf6e7eae and < ea5fe6a73ca57e5150b8a38b341aef2636eb72f0
- affected6.4
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.