dbcve.org
Modicon M241 FirmwareOperating system · Schneider Electric

CVE-2017-6028

CRITICAL · 9.8 CVSS v3.1 Published 2017-06-30
Fix available
A fix is available. Upgrade to after 4.0.3.20 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An Insufficiently Protected Credentials issue was discovered in Schneider Electric Modicon PLCs Modicon M241, all firmware versions, and Modicon M251, all firmware versions. Log-in credentials are sent over the network with Base64 encoding leaving them susceptible to sniffing. Sniffed credentials could then be used to log into the web application.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Insufficiently Protected Credentials vulnerability in Schneider Electric Modicon M241 and M251 PLCs where user login credentials are transmitted over the network using Base64 encoding (a reversible encoding, not encryption). An attacker with network access can sniff these encoded credentials, decode them trivially using Base64 decoding, and use them to authenticate to the PLC web application.

MitigationImplement TLS/SSL encryption for all web application traffic to protect credentials in transit. Additionally, restrict network access to the PLCs through network segmentation and firewall rules to prevent unauthorized sniffing.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Modicon M241 FirmwareOperating system
Affected:<= 4.0.3.20
Modicon M251 FirmwareOperating system
Affected:<= 4.0.3.20

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify PLC model
    Access the PLC web interface or check device documentation/labels to confirm the model is Modicon M241 or Modicon M251
    Affected if The device is a Modicon M241 or M251 PLC
  2. Check firmware version
    Log into the PLC web application and navigate to the firmware/version information section, or use Schneider Electric's programming software (SoMachine or EcoStruxure) to query the device firmware version
    Affected if Firmware version is 4.0.3.20 or lower
  3. Verify web access protocol
    Attempt to access the PLC web interface via HTTP (port 80) rather than HTTPS (port 443)
    Affected if The web application is accessible over unencrypted HTTP
  4. Inspect network traffic
    Use a network packet capture tool (such as Wireshark) to capture traffic during a login attempt to the PLC web interface and examine if credentials are sent as Base64-encoded plaintext rather than encrypted TLS traffic
    Affected if Login credentials are transmitted as Base64-encoded strings in cleartext network packets

Your environment is affected if you have a Modicon M241 or M251 PLC running firmware version 4.0.3.20 or lower with its web interface accessible over unencrypted HTTP, allowing credentials to be captured and decoded from network traffic.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 4.0.3.20
Interim mitigation

Implement TLS/SSL encryption for all web application traffic to protect credentials in transit. Additionally, restrict network access to the PLCs through network segmentation and firewall rules to prevent unauthorized sniffing.

Recommended fix Moderate confidence

Firmware version > 4.0.3.20 (contact Schneider Electric for specific fixed release)

  1. 1. Identify the current firmware version of the Modicon M241 or M251 PLC by accessing the web application or using Schneider Electric's programming software.
  2. 2. Navigate to the Schneider Electric download page for Modicon M241/M251 PLCs and check for firmware versions later than 4.0.3.20.
  3. 3. Download the latest available firmware version from Schneider Electric's official support website (www.schneider-electric.com).
  4. 4. Review the firmware release notes to confirm the version includes a fix for CVE-2017-6028.
  5. 5. Backup the PLC project/program and configuration before performing the firmware update.
  6. 6. Follow Schneider Electric's official firmware update procedure to upgrade the PLC to a version newer than 4.0.3.20.
  7. 7. After upgrading, verify that web application credentials are now transmitted using proper encryption (not just Base64 encoding).
Caveat Review release notes for any changes to functionality or configuration that may require project modifications after firmware upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Modicon M241 Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA3.0 h
18.0 hours of engineering $3,180
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2017-6028 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2017-6028 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data