---
id: CVE-2026-102509
title: >-
  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…
summary: >-
  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…
severity: high
cvss: 8.7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-674
  - CWE-770
  - CWE-789
vendor: Apache Software Foundation
product: 'org.apache.plc4x:plc4j-spi'
affected:
  - 'org.apache.plc4x:plc4j-spi >= 0.10.0 < 1.0.0'
  - 'org.apache.plc4x:plc4j-driver-opcua >= 0.10.0 < 1.0.0'
published: '2026-09-30'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T09:17:14.100'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102509'
references:
  - url: 'https://lists.apache.org/thread.html/qngc85qhnlj7kpk3z58z0xlxhz2tn6gp'
    label: security@apache.org
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-30T09:00:29.916Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.