CVE-2021-33486Network attack vector

Remote service interruption via socket exhaustion mishandling

Published Aug 3, 2021 · Updated Aug 3, 2024

Improper exception handling in CODESYS V3 Runtime Toolkit for VxWorks before 3.5.17.10 allows remote attackers to interrupt service. The VxWorks platform adaptation layer mishandles socket exhaustion, disconnecting existing socket connections and preventing reconnection for a period. Affected releases begin at 3.5.8.0, and no authentication or user interaction is required; affected servers include OPC UA and the UDP communication driver.

CVSS severity7.5
High
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper exception handling in CODESYS V3 Runtime Toolkit for VxWorks before 3.5.17.10 allows remote attackers to interrupt service. The VxWorks platform adaptation layer mishandles socket exhaustion, disconnecting existing socket connections and preventing reconnection for a period. Affected releases begin at 3.5.8.0, and no authentication or user interaction is required; affected servers include OPC UA and the UDP communication driver.

The record

CVE
CVE-2021-33486
Published
Aug 3, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-755, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5CODESYS GmbHCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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