What is the CVSS score of CVE-2026-67861?

CVE-2026-67861 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.4%.

Which versions of open62541 are affected by CVE-2026-67861?

Open62541 v1.5.5 and earlier, an OPC UA industrial communication library widely deployed in SCADA and manufacturing systems, contains a remote denial-of-service vulnerability that allows…

How to fix or mitigate CVE-2026-67861?

Within 24 hours, inventory all systems running open62541 v1.5.5 or earlier and identify which support active OPC UA connections from external or untrusted networks. Within 7 days, implement network-level controls by restricting inbound OPC UA traffic (port 4840/TCP) to whitelisted trusted sources only and configure firewall rules to block unsolicited connections; additionally, enable any available connection rate-limiting or input validation mechanisms in your OPC UA gateway or supervisory systems. Within 30 days, coordinate with vendors and integrators to define a patching timeline for versions after v1.5.5, validate incident response procedures for client unavailability scenarios, and establish automated monitoring for unexpected client process crashes correlated with network anomalies.

open62541 CVE-2026-67861

EUVD-2026-52963 HIGH

Uncontrolled Resource Consumption (CWE-400)

2026-08-04 mitre

GHSA-5hm6-mc9f-6w2p

Denial Of Service N A

7.5

CVSS 3.1 · Vendor: mitre

Severity by source

Vendor (mitre) PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

vuln.today AI

7.5 HIGH

Network-accessible client function exploitable via malicious server response, no credentials needed, availability-only impact consistent with crash/DoS.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Red Hat

7.5 HIGH

qualitative

Primary rating from Vendor (mitre).

CVSS VectorVendor: mitre

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Aug 05, 2026 - 00:07 vuln.today

CVE Published

Aug 04, 2026 - 00:00 cve.org

HIGH 7.5

DescriptionCVE.org

An issue in open62541 v.1.5.5 and before allows a remote attacker to cause a denial of service via the UA_Client_getRemoteDataTypes component

AnalysisAI

Denial of service in open62541 v1.5.5 and earlier allows a remote unauthenticated attacker to crash an affected client via a malformed or malicious response processed by the UA_Client_getRemoteDataTypes function. open62541 is an open-source C implementation of the OPC UA industrial communication protocol, making this vulnerability relevant to ICS, SCADA, and industrial IoT deployments. No public exploit code has been explicitly confirmed, but a GitHub issue (open62541/open62541#8140) documents the flaw, and no actively exploited status (KEV) has been assigned at time of analysis.

Technical ContextAI

open62541 is a widely-adopted open-source OPC UA (OPC Unified Architecture, IEC 62541) stack implemented in C, used for machine-to-machine communication in industrial automation, manufacturing, and IoT environments. The vulnerable component, UA_Client_getRemoteDataTypes (located in src/client/ua_client_util.c per the referenced source), is responsible for querying and parsing custom data type definitions from a remote OPC UA server during session setup or browsing. The custom_datatype client example (examples/custom_datatype/client_types_custom.c) is also referenced, suggesting the flaw may manifest during custom data type negotiation. CWE classification was not provided, but the availability-only impact profile (C:N/I:N/A:H) combined with a network vector strongly suggests a memory safety flaw such as a null pointer dereference, use-after-free, or uncontrolled resource consumption triggered by crafted server responses. CPE data was not populated by NVD (cpe:2.3:a:n/a:n/a), so affected product scope is derived solely from the CVE description.

RemediationAI

No vendor-released patch version has been independently confirmed at time of analysis. The CVE references point to a GitHub issue (https://github.com/open62541/open62541/issues/8140) and source files tagged at v1.5.5, but no merged fix commit or tagged release containing a patch was identified in the provided data. Developers and operators should monitor the open62541 GitHub repository for a patch release beyond v1.5.5 and upgrade as soon as one is available. As a compensating control, restrict open62541 client instances to connect only to known, trusted OPC UA servers by enforcing certificate-based authentication and TLS (OPC UA SecureChannel with SignAndEncrypt mode), which prevents a rogue server from triggering the flaw without first compromising a trusted endpoint. Additionally, network-level controls such as OPC UA traffic filtering (default TCP port 4840) and network segmentation can limit the attack surface to trusted industrial network segments. These mitigations reduce but do not eliminate risk if the trusted server itself is compromised.