Linux kernel bug affects widespread OS kernels, can crash or enable local kernel compromise; high-impact for any org running Linux.
CVE-2026-64459
Local kernel memory corruption/privilege escalation via TCP-AO/TCP-MD5 RCU bug
Is CVE-2026-64459 being exploited?
Not confirmed. CVE-2026-64459 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 0.47% probability of exploitation in the next 30 days.
How severe is CVE-2026-64459?
CVE-2026-64459 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-2026-64459?
Yes. A fix has been recorded for CVE-2026-64459. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64459 affect?
CVE-2026-64459 affects Linux kernel (net/ipv4 tcp_ao / tcp_output), Any Linux distro using upstream kernels unless backported. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64459?
Install kernel update/backport; disable TCP-AO/TCP-MD5 and restrict unprivileged user namespaces until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local attacker can trigger kernel memory corruption leading to crashes and potential local privilege escalation via crafted TCP-AO/TCP-MD5 during connect.
Immediate action required
- affected>= 51e547e8c89c661f6fbede4a28b1d33b13625683 and < 657646c08c94ef7b9dbe468fe7828032216f9841
- affected>= 51e547e8c89c661f6fbede4a28b1d33b13625683 and < 4caf12c778fed3dc3824cf36263be5e2c491fbd0
- affected>= 51e547e8c89c661f6fbede4a28b1d33b13625683 and < 8bc4d43bccbd60efe85d0a44d5bf41762f2f0c30
- affected6.18
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.