CVE-2026-27663Public exploit

Parameterization denial via unthrottled remote-operation requests

Published Mar 26, 2026 · Updated Mar 26, 2026

Resource exhaustion in Siemens CPCI85 and RTUM85 before 26.10 allows remote attackers on an adjacent network to interrupt parameterization. The remote-operation endpoint accepts repeated POST requests with attacker-controlled session and length values without limiting request-driven resource consumption. Fewer than 100 requests can stall the service until it is restarted through the web interface or the device is rebooted; the PLC remains running, but Toolbox II can no longer set parameters.

CVSS severity7.1
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Siemens CPCI85 and RTUM85 before 26.10 allows remote attackers on an adjacent network to interrupt parameterization. The remote-operation endpoint accepts repeated POST requests with attacker-controlled session and length values without limiting request-driven resource consumption. Fewer than 100 requests can stall the service until it is restarted through the web interface or the device is rebooted; the PLC remains running, but Toolbox II can no longer set parameters.

The record

CVE
CVE-2026-27663
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Siemens
Product
RTUM85 RTU Base
Classifications
CWE-770, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <V26.10

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Siemens · RTUM85 RTU Baseversion=0 <V26.10
Siemens · CPCI85 Central Processing/Communicationversion=0 <V26.10

Published CVSS scores

6.5Siemens ProductCERTCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.1Siemens ProductCERTCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

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

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
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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