Executive brief
A vulnerability in the open62541 library, an open-source implementation of the OPC UA industrial communication standard, allows an attacker to crash or disable a server. By sending specially crafted requests that lack size limits, an attacker can force the server to consume all available memory. This can lead to a total service outage, disrupting industrial operations and monitoring without requiring any user credentials.
Technical details
A denial-of-service vulnerability exists in open62541 due to improper validation of the 'serverUris' field within a 'FindServersRequest'. An unauthenticated remote attacker can initiate a pre-session request and declare an arbitrarily large string (up to ~3.9 GB) delivered across multiple intermediate chunks. Because the server does not validate the array size or string length and buffers all chunks in RAM until the SecureChannel times out, an attacker can exhaust available system memory. This bypasses encryption configurations as it occurs before session establishment. The issue has been addressed by enforcing default message and chunk size limits (e.g., 512 MB per message and 16384 chunks) when configurations are set to zero.
Affected products
- open62541 project / o6 Automation GmbH open62541 1.4.0 through 1.4.16, 1.5.0 through 1.5.4, master
Timeline
- 2026-06-23: patched: Fix merged into 1.4 branch via Pull Request 8142
- 2026-07-02: disclosed: CVE published to NVD