Core OS kernel vulnerability; affects Linux kernel across distributions; could enable LPE and data leakage in multi-namespace setups.
CVE-2026-43403
Linux kernel LPE via nsfs namespace IOCTLs.
Is CVE-2026-43403 being exploited?
Not confirmed. CVE-2026-43403 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-2026-43403?
CVE-2026-43403 is rated High with a CVSS score of 8.8. 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-2026-43403?
Yes. A fix has been recorded for CVE-2026-43403. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-43403 affect?
CVE-2026-43403 affects Linux kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-43403?
Update to patched kernel version
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local privilege escalation; could leak namespace data and gain higher privileges via nsfs IOCTLs.
Patch when possible
- affected>= a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 and < 3376b345df155ca36d8611857b41ff7d5183fc38
- affected>= a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 and < 2f3dea284c761c890d676f77d5e55c0c496b4ef4
- affected>= a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 and < 0ad650e60150eda789deca5e78a6a09d26bf8fc9
- affected>= a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 and < e6b899f08066e744f89df16ceb782e06868bd148
- affected6.12
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.