CVE-2020-24686Network attack vector

Web visualization outage via request and ping floods

Published Feb 26, 2021 · Updated Aug 4, 2024

Denial of service in ABB AC500 V2 PLCs with onboard Ethernet allows remote attackers to interrupt web visualization through network floods. The enabled unauthenticated web interface stops serving valid requests after rapid arbitrarily long URL requests, while sustained ICMP pings make the Web HMI unresponsive until the PLC is restarted. Exposure requires the optional web server to be enabled and network-reachable; remote visibility and Automation Builder connections fail, but the PLC application continues running.

CVSS severity7.5
High
EPSS probability1.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in ABB AC500 V2 PLCs with onboard Ethernet allows remote attackers to interrupt web visualization through network floods. The enabled unauthenticated web interface stops serving valid requests after rapid arbitrarily long URL requests, while sustained ICMP pings make the Web HMI unresponsive until the PLC is restarted. Exposure requires the optional web server to be enabled and network-reachable; remote visibility and Automation Builder connections fail, but the PLC application continues running.

The record

CVE
CVE-2020-24686
Published
Feb 26, 2021
Updated
Aug 4, 2024
Vendor
ABB
Product
AC500
Classifications
CWE-400, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

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  1. Affected versionversion=All

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ABB · AC500version=All

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5ABBCVSS:3.1/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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