What is the CVSS score of CVE-2026-67859?

CVE-2026-67859 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: 0.5%.

Which versions of open62541 are affected by CVE-2026-67859?

A remote denial-of-service vulnerability in open62541 v1.5.5 allows unauthenticated attackers to crash the OPC UA Discovery Server, causing complete service unavailability.

How to fix or mitigate CVE-2026-67859?

Within 24 hours: Inventory all systems running open62541 v1.5.5 and document their network accessibility and operational criticality. Within 7 days: Implement network segmentation to restrict access to OPC UA Discovery Server ports (typically 4840) to only authorized clients; deploy firewall rules to block unauthenticated discovery requests where possible; enable enhanced monitoring and alerting for abnormal OPC UA traffic patterns. Within 30 days: Monitor vendor advisories for an available patch; when released, schedule a staged upgrade to a patched version confirmed from open62541 project security advisories.

open62541 CVE-2026-67859

EUVD-2026-52994 HIGH

Classic Buffer Overflow (CWE-120)

2026-08-04 cve@mitre.org

GHSA-2v4p-65pc-4gv4

Buffer Overflow Denial Of Service

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

OPC UA Discovery accepts unauthenticated network traffic by protocol design, so PR:N and AV:N are appropriate; impact is availability-only with no confidentiality or integrity effect.

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

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 - 00:36 vuln.today

CVE Published

Aug 04, 2026 - 22:17 cve.org

HIGH 7.5

DescriptionCVE.org

Buffer Overflow vulnerability in open62541 v1.5.5 allows a remote attacker to cause a denial of service via the Discovery/LDS handling.

AnalysisAI

Remote denial-of-service in open62541 v1.5.5 is achievable by exploiting a buffer overflow in the OPC UA Discovery/Local Discovery Server (LDS) handling code. An unauthenticated remote attacker can send a specially crafted OPC UA discovery request to crash the affected server process, resulting in full availability loss. No public exploit code has been confirmed and this vulnerability has not been added to the CISA KEV catalog at the time of analysis.

Technical ContextAI

open62541 is an open-source C-language implementation of the OPC UA (Open Platform Communications Unified Architecture) protocol, widely used in industrial control systems, manufacturing automation, and IoT edge devices. The vulnerability resides specifically in the Discovery and Local Discovery Server (LDS) subsystem, as evidenced by the referenced source files ua_discovery_mdns.c, ua_services_discovery.c, server_lds.c, and ua_util.c. OPC UA Discovery allows clients to locate available servers on a network - this is a standard, often network-exposed feature. The root cause is a buffer overflow (consistent with the Tags field), meaning attacker-controlled input exceeding allocated buffer bounds corrupts adjacent memory. No CWE was formally assigned, but the behavior maps most closely to CWE-120 (Buffer Copy without Checking Size of Input) or CWE-122 (Heap-based Buffer Overflow). The impact is limited to availability (C:N/I:N/A:H per CVSS), indicating the overflow triggers a crash or uncontrolled termination rather than code execution.

RemediationAI

No vendor-released patch version has been identified at time of analysis; the references point only to source code files and a GitHub issue tracker entry (https://github.com/open62541/open62541/issues/8095), not to a tagged release or formal advisory. Operators should monitor the upstream repository and issue #8095 for patch availability. As an immediate compensating control, restrict network access to OPC UA Discovery and LDS endpoints (default TCP port 4840) to trusted clients only using firewall rules or network segmentation - this reduces the attack surface since exploitation requires network reachability. If LDS/Discovery server functionality is not operationally required, disable or do not instantiate the LDS server component in the application. Note that disabling discovery will prevent OPC UA clients from auto-locating the server, requiring hardcoded endpoint configuration. Upgrade open62541 to a patched release as soon as one becomes available.