Is CVE-2026-18784 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-18784 being exploited in the wild.

How severe is CVE-2026-18784?

Medium severity, with a CVSS score of 5.3, published 4 August 2026.

Which products and versions are affected?

open62541 open62541 up to 1.5.5.

Is there a fix for CVE-2026-18784?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-18784 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-18784?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-18784: open62541 heap buffer overflow in UA_Client_readNodeClassAttribute

CVE-2026-18784 · Severity: medium · CVSS 5.3 · Published 2026-08-04

open62541 is an open-source OPC UA library used in industrial control systems, gateways, and diagnostic tools to communicate with servers. A malicious OPC UA server can trigger a heap-based buffer over-read in the client library when reading node class attributes, causing the client process to crash and resulting in denial of service of critical industrial infrastructure components.

Quick answers

Is CVE-2026-18784 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-18784 being exploited in the wild.
How severe is CVE-2026-18784?: Medium severity, with a CVSS score of 5.3, published 4 August 2026.
Which products and versions are affected?: open62541 open62541 up to 1.5.5.
Is there a fix for CVE-2026-18784?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-18784 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-18784?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A heap buffer over-read exists in the __Client_readAttribute() function in src/client/ua_client_highlevel.c. The vulnerable code path for UA_ATTRIBUTEID_NODECLASS skips type validation and unconditionally reads sizeof(UA_NodeClass) bytes (4 bytes) from a variant field without confirming the variant actually contains a NodeClass type. If a malicious server responds with a Boolean (1 byte) instead, a 4-byte out-of-bounds read occurs. The attack is reachable via a real OPC UA TCP handshake (HEL/ACK → OpenSecureChannel → FindServers → GetEndpoints → Read). The primary impact is remote denial of service; industrial clients connecting to untrusted or compromised servers are at risk. Patches are expected from the open62541 project.

Affected products

open62541 open62541 up to 1.5.5

Timeline

2026-08-04: disclosed: Published on NVD
2026: other: Exploit made public; project report closed, stating not official reporting channel

References

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