# CVE-2026-67862: open62541 heap-buffer-overflow in high-level attribute reading

Source: https://junglewise.ai/threats/cve-2026-67862-open62541-heap-buffer-overflow-in-high-level-attribute-reading  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-04. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-67862 · Severity: high · CVSS 7.5 · Published 2026-08-04

open62541 is a widely-used OPC UA protocol library that industrial systems, gateways, and diagnostic tools use to connect to manufacturing and infrastructure equipment. A malicious or compromised OPC UA server can trigger an out-of-bounds memory read in a client library function that retrieves node class attributes, causing the client process to crash and denying service to critical operational components.

## Quick answers

**Is CVE-2026-67862 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-67862 being exploited in the wild.

**How severe is CVE-2026-67862?** High severity, with a CVSS score of 7.5, published 4 August 2026.

**Which products and versions are affected?** open62541 open62541 1.5.5.

**Is there a fix for CVE-2026-67862?** 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-2026-67862 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-67862?** 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

The vulnerability is a heap-buffer-overflow in the __Client_readAttribute() function in src/client/ua_client_highlevel.c when reading the UA_ATTRIBUTEID_NODECLASS attribute. The vulnerable code performs a fixed 4-byte memcpy from res->value.data without validating that the server returned the expected NodeClass type; it skips the scalar-type validation checks applied to other attributes. A malicious server responding to a Read(NodeClass) request with a Boolean-typed Variant (memSize=1) instead triggers a 4-byte out-of-bounds heap read. The attack is reachable through standard OPC UA TCP negotiation and does not require special authentication. Impact is confirmed remote denial of service of client applications.

## Affected products

- open62541 open62541 1.5.5

## Timeline

- 2026-08-04: disclosed

## References

- [https://github.com/open62541/open62541/blob/v1.5.5/src/client/ua_client_highlevel.c](https://github.com/open62541/open62541/blob/v1.5.5/src/client/ua_client_highlevel.c)
- [https://github.com/open62541/open62541/issues/8139](https://github.com/open62541/open62541/issues/8139)