CVE-2026-71263
Unauthenticated Modbus TCP buffer overflow in FreeModbus LINUXTCP port.
Is CVE-2026-71263 being exploited?
Not confirmed. CVE-2026-71263 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 0.28% probability of exploitation in the next 30 days.
How severe is CVE-2026-71263?
CVE-2026-71263 is rated Critical with a CVSS score of 9.1. 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-2026-71263?
Not known from our data. No patch reference has been recorded for CVE-2026-71263, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-71263 affect?
CVE-2026-71263 affects FreeModbus LINUXTCP port (demo/LINUXTCP/port/porttcp.c), Devices using FreeModbus for Modbus TCP (PLCs, RTUs, gateways), Embedded/OT devices bundling FreeModbus. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-71263?
Block Modbus TCP (port 502) from untrusted networks; apply vendor patch when available and monitor for exploit attempts.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated remote memory corruption via a crafted Modbus TCP packet, enabling crash (DoS) or potential remote code execution on affected devices.
Immediate action required
- affected<= *
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.