Pre-auth resource-exhaustion (memory/stack) in Apache PLC4X OPC UA driver can remotely DoS industrial/OT systems across sectors; impacts widely used PLC4X deployments and can disrupt operations.
CVE-2026-102509
Pre-auth memory/stack exhaustion in Apache PLC4X OPC UA driver allows remote DoS.
Is CVE-2026-102509 being exploited?
Not confirmed. CVE-2026-102509 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 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-102509?
CVE-2026-102509 is rated High with a CVSS score of 8.7. 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-2026-102509?
Yes. A fix has been recorded for CVE-2026-102509. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-102509 affect?
CVE-2026-102509 affects Apache PLC4X (Java) 0.10.0 - <1.0.0, OPC UA driver (pre-auth), PLC4X generated protocol parsers (Java). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-102509?
Upgrade Apache PLC4X to 1.0.0; block/untrusted OPC UA endpoints and monitor connections.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Pre-auth remote resource exhaustion (memory, heap, stack) and uncontrolled recursion causing denial of service by impersonated/malicious OPC UA servers.
Immediate action required
- affected>= 0.10.0 and < 1.0.0
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.