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RealportApplication · Digi

CVE-2021-35979

HIGH · 8.1 CVSS v3.1 Published 2021-10-08
Fix available
A fix is available. Upgrade to after 4.8.488.0 or later.
See remediation →
90/100
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 issue was discovered in Digi RealPort through 4.8.488.0. The 'encrypted' mode is vulnerable to man-in-the-middle attacks and does not perform authentication.

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 · moderate confidence

Digi RealPort versions through 4.8.488.0 contain a vulnerability in the 'encrypted' mode where man-in-the-middle attacks are possible due to the lack of proper authentication. The encryption implementation fails to validate endpoints, allowing attackers to intercept and potentially modify communications between clients and the serial-to-Ethernet device.

MitigationImplement mutual authentication and proper certificate validation in the encrypted mode to prevent MITM attacks. Until a patch is available, avoid using the 'encrypted' mode over untrusted networks and consider network segmentation as a compensating control.

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
RealportApplication
Affected:<= 1.9-40<= 4.8.488.0
Connectport Ts 8\/16 FirmwareOperating system
Affected:all versions
Connectport Lts 8\/16\/32 FirmwareOperating system
Affected:all versions
Passport Integrated Console Server FirmwareOperating system
Affected:all versions
Cm FirmwareOperating system
Affected:all versions
Portserver Ts FirmwareOperating system
Affected:all versions
Portserver Ts Mei FirmwareOperating system
Affected:all versions
Portserver Ts Mei Hardened FirmwareOperating system
Affected:all versions

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/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 Digi RealPort software installation
    Check the system for Digi RealPort software by looking for the executable (typically at C:\Program Files\Digi\RealPort\RealPort.exe on Windows or /usr/sbin/RealPort on Linux) or check the installed programs list
    Affected if Digi RealPort software is installed with version <= 1.9-40 or <= 4.8.488.0
  2. Verify RealPort version
    Run 'RealPort -v' or right-click the RealPort.exe file and select Properties > Details to view the version number
    Affected if The installed version is 1.9-40 or lower, or 4.8.488.0 or lower
  3. Determine if encrypted mode is enabled
    Inspect the RealPort configuration file (usually realport.cfg in the installation directory or /etc/realport.conf on Linux) or check the RealPort service settings for the 'encrypted' parameter
    Affected if Encrypted mode is configured and enabled in the RealPort configuration
  4. Identify Digi hardware devices on the network
    Scan the network for Digi device types: Connectport TS 8/16, Connectport LTS 8/16/32, Passport, CM, Portserver TS, or Portserver TS Mei using network discovery tools or by checking device web interfaces
    Affected if Any of the listed Digi hardware devices (Connectport TS, Connectport LTS, Passport, CM, Portserver TS, or Portserver TS Mei) are deployed on the network
  5. Check hardware firmware versions
    Access the admin web interface of the Digi device and navigate to the firmware or status page to view the current firmware version
    Affected if The device firmware is any version (all versions of these products are affected according to the advisory)

You are affected if you run Digi RealPort software version <= 1.9-40 or <= 4.8.488.0 with encrypted mode enabled, or if you have any of the listed Digi hardware devices (Connectport TS/LTS, Passport, CM, Portserver TS series) deployed regardless of firmware version.

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.

From vendor data
Upgrade available Upgrade to a release after 4.8.488.0
Interim mitigation

Implement mutual authentication and proper certificate validation in the encrypted mode to prevent MITM attacks. Until a patch is available, avoid using the 'encrypted' mode over untrusted networks and consider network segmentation as a compensating control.

Fix this in Realport Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA3.0 h
19.0 hours of engineering $3,380
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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-2021-35979 in production — separate from our analysis above.

No notes yet

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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