CVE-2026-18784Public exploitNetwork attack vector

Client crash via unchecked NodeClass response type

Published Aug 4, 2026 · Updated Aug 4, 2026

Heap out-of-bounds read in open62541 1.5.0 through 1.5.5 allows remote attackers to crash clients via malicious OPC UA responses. The __Client_readAttribute helper copies four bytes for NodeClass without confirming that the decoded Variant is scalar and has the NodeClass type. Exploitation requires a client application to call UA_Client_readNodeClassAttribute while connected to an attacker-controlled or compromised OPC UA server.

CVSS severityUnavailable
Unscored
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap out-of-bounds read in open62541 1.5.0 through 1.5.5 allows remote attackers to crash clients via malicious OPC UA responses. The __Client_readAttribute helper copies four bytes for NodeClass without confirming that the decoded Variant is scalar and has the NodeClass type. Exploitation requires a client application to call UA_Client_readNodeClassAttribute while connected to an attacker-controlled or compromised OPC UA server.

The record

CVE
CVE-2026-18784
Published
Aug 4, 2026
Updated
Aug 4, 2026
Vendor
o6 Automation GmbH
Product
open62541
Classifications
CWE-122, CWE-119, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.5.0
  2. Affected versionversion=1.5.1
  3. Affected versionversion=1.5.2
  4. Affected versionversion=1.5.3
  5. Affected versionversion=1.5.4
  6. Affected versionversion=1.5.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

o6 Automation GmbH · open62541version=1.5.0; version=1.5.1; version=1.5.2; version=1.5.3; version=1.5.4; version=1.5.5

Published CVSS scores

4.3VulDB CNAAV:L/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR
5.3VulDB CNACVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R
4.8VulDB CNACVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
5.3VulDB CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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