Kernel-level network filter bypass in widely-deployed Linux (io_uring/net) can evade network policy and container/sandbox restrictions across enterprises.
CVE-2026-99042
Linux kernel io_uring IPv6 connect BPF filter bypass allows blocked connections.
Is CVE-2026-99042 being exploited?
Not confirmed. CVE-2026-99042 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 0.16% probability of exploitation in the next 30 days.
How severe is CVE-2026-99042?
CVE-2026-99042 is rated High with a CVSS score of 8.4. 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-2026-99042?
Yes. A fix has been recorded for CVE-2026-99042. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-99042 affect?
CVE-2026-99042 affects Linux kernel (io_uring/net), Kernels with vulnerable io_connect_bpf handling (pre-patch; see vendor). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-99042?
Apply vendor/kernel updates or upstream patch immediately; restrict untrusted code until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypasses BPF/socket connect filters for IPv6 (24-byte sockaddr_in6), permitting connections to addresses/ports that should be blocked; enables network policy evasion from local processes/containers.
Patch when possible
- affected>= 899bea8248cee35d54760a5e7d61a76af8e64411 and < 596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5
- affected>= 899bea8248cee35d54760a5e7d61a76af8e64411 and < aa5d5f8e502318e783545ba5d04bb40130b83e20
- affected7.2
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.