CVE-2024-8935Public exploitNetwork attack vector

Controller session hijacking via unauthenticated Diffie-Hellman exchange

Published Nov 13, 2024 · Updated Nov 13, 2024

Authentication bypass in Schneider Electric Modicon controllers allows man-in-the-middle attackers to hijack privileged UMAS sessions. The unauthenticated Diffie-Hellman exchange lets attackers decrypt both session nonces and calculate signatures for reserved UMAS messages. Attackers must occupy the logical network while a valid engineering-workstation session is established, after which forged privileged messages can expose or alter controller data or interrupt service.

CVSS severity7.5
High
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Schneider Electric Modicon controllers allows man-in-the-middle attackers to hijack privileged UMAS sessions. The unauthenticated Diffie-Hellman exchange lets attackers decrypt both session nonces and calculate signatures for reserved UMAS messages. Attackers must occupy the logical network while a valid engineering-workstation session is established, after which forged privileged messages can expose or alter controller data or interrupt service.

The record

CVE
CVE-2024-8935
Published
Nov 13, 2024
Updated
Nov 13, 2024
Vendor
Distributed Data Systems
Product
Modicon M340 BMXP341000
Classifications
CWE-290, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 13, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 13, 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?

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

  1. Affected versionversion=SV3.60 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Distributed Data Systems · Modicon M340 BMXP341000version=SV3.60 <*
Distributed Data Systems · Modicon Momentum Unity M1E Processorversion=0 <*; version=All Versions
Distributed Data Systems · Modicon MC80 BMKC8020301version=0 <*
Distributed Data Systems · Modicon MC80version=All versions
Distributed Data Systems · Modicon M340 CPUversion=All versions since SV3.60

Published CVSS scores

7.7Schneider Electric SECVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
7.5Schneider Electric SECVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/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 exploitPublished

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
T1557Adversary-in-the-Middle

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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