CVE-2026-102509: Apache PLC4X, Apache PLC4X: Pre-authentication resource exhaustion in the OPC UA driver and the Java SPI parser
Memory Allocation with Excessive Size Value, Allocation of Resources Without Limits, and Uncontrolled Recursion in the Java implementation of Apache PLC4X (PLC4J) allow a malicious or impersonated device to exhaust the memory or stack of the client application, causing a denial of service.
In the OPC UA driver these defects are reachable before authentication: the offending data is parsed while the secure channel and session are being established, before the server's identity has been bound to it. Configuring a trusted server therefore does not prevent exploitation by an attacker who can impersonate it.
The individual defects are: - Length-prefixed byte strings are allocated at the size claimed on the wire before the length is checked against the data actually received (0.10.0 through 0.13.1). - Array fields in generated protocol parsers pre-allocate a list with the element count claimed on the wire, allowing a single count field to trigger a multi-gigabyte allocation. This parser is shared by all PLC4J drivers; the OPC UA driver is the verified pre-authentication path (0.10.0 through 0.13.1). - The OPC UA driver accumulates message chunks without enforcing the negotiated maximum chunk count and message size (0.12.0 through 0.13.1). - The OPC UA driver pre-allocates collections using element counts received from the server (0.10.0 through 0.13.1). - Recursive protocol types are parsed without a nesting-depth limit. The same defect in the Go implementation is covered by CVE-2026-102510 https://cveprocess.apache.org/cve5/CVE-2026-102510 .
This issue affects Apache PLC4X: from 0.10.0 before 1.0.0.
Users are recommended to upgrade to version 1.0.0, which fixes the issue.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache PLC4Xto a version that resolves this vulnerability.Fixed in 1.0.0
Event History
Frequently Asked Questions
Which deployments should be prioritized for assessment?
Java-based Apache PLC4X (PLC4J) deployments using versions 0.10.0 through 0.13.1 should be assessed. The OPC UA driver has a verified pre-authentication exposure path; the affected generated parser is shared by all PLC4J drivers, although only OPC UA is identified as a verified pre-authentication path.
Does configuring a trusted OPC UA server prevent exploitation?
No. The affected data is parsed while the secure channel and session are being established, before the server identity is bound, so an attacker that can impersonate the server can exploit the issue despite a trusted-server configuration.
What must an attacker be able to do?
The attacker needs to operate a malicious device or impersonate one and provide crafted protocol data to the client. The malformed data can cause excessive memory allocation, unbounded resource use, or stack exhaustion, resulting in denial of service.