Core Linux kernel vulnerability affecting widespread kernel deployments; kernel privilege escalation risk.
CVE-2026-43503
Linux kernel frag-transfer frag-marker bug enables local privilege escalation
Is CVE-2026-43503 being exploited?
Not confirmed. CVE-2026-43503 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 0.34% probability of exploitation in the next 30 days.
How severe is CVE-2026-43503?
CVE-2026-43503 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-2026-43503?
Yes. A fix has been recorded for CVE-2026-43503. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-43503 affect?
CVE-2026-43503 affects Linux kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-43503?
Update to patched kernel version
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unprivileged user can gain kernel privileges by manipulating frag transfer markers in skb handling to access/write root-owned page cache.
Immediate action required
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < fbeab9555564a1b98e8582cd106dfe46c4606991
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < 179f1852bdedc300e373e807cc102cd81feff196
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < 12401fcfb01f53ccc63ab0a3246570fe8f3105ee
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < 989214c66884d70716d83dc1d0bf5e16287bf349
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < ff375cc75f9167168db38e0464a482d5fbc8d81d
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < 9bc9d6d6967a2239aa57af2aa53554eddd640d20
- affected>= cef401de7be8c4e155c6746bfccf721a4fa5fab9 and < 48f6a5356a33dd78e7144ae1faef95ffc990aae0
- affected3.9
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.