CVE-2023-28531Network attack vector

Unauthorized smartcard key use via dropped destination constraints

Published Mar 17, 2023 · Updated Sep 8, 2026

Improper access control in OpenSSH 8.9 through 9.2 on Siemens MFP controllers allows attackers to use smartcard keys beyond intended hops. ssh-add fails to pass -h per-hop destination constraints to ssh-agent when adding smartcard keys, so the agent stores those keys without the requested restrictions. Exploitation requires access to an agent holding such a constrained smartcard key; ordinary keys and unconstrained additions are unaffected.

CVSS severity9.8
Critical
EPSS probability2.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in OpenSSH 8.9 through 9.2 on Siemens MFP controllers allows attackers to use smartcard keys beyond intended hops. ssh-add fails to pass -h per-hop destination constraints to ssh-agent when adding smartcard keys, so the agent stores those keys without the requested restrictions. Exploitation requires access to an agent holding such a constrained smartcard key; ordinary keys and unconstrained additions are unaffected.

The record

CVE
CVE-2023-28531
Published
Mar 17, 2023
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-311, CWE-284, T1552.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 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=V3.1.5 <*
  2. Affected versionversion=V3.1.6 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.5 <*; version=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.5 <*; version=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.5 <*; version=V3.1.6 <*

Published CVSS scores

9.8Siemens ProductCERTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-311Missing Encryption of Sensitive Data
CWE-284Improper Access Control
T1552.004Unsecured Credentials: Private Keys

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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