dbcve.org
RealportApplication · Digi

CVE-2021-35977

CRITICAL · 9.8 CVSS v3.1 Published 2021-10-08
Fix available
A fix is available. Upgrade to after 4.8.488.0 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 issue was discovered in Digi RealPort for Windows through 4.8.488.0. A buffer overflow exists in the handling of ADDP discovery response messages. This could result in arbitrary code execution.

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

A buffer overflow vulnerability exists in Digi RealPort for Windows (versions up to 4.8.488.0) in the parsing component that handles ADDP (Advanced Device Discovery Protocol) discovery response messages. By sending a specially crafted response with oversized data, an unauthenticated attacker can overwrite memory buffers and achieve arbitrary code execution with elevated privileges.

MitigationApply the vendor-provided patch or update Digi RealPort to a version beyond 4.8.488.0. If patching is not immediately possible, restrict network access to trusted sources and disable ADDP discovery on untrusted segments to reduce attack surface.

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
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 Digi RealPort installation on Windows
    Check for the presence of Digi RealPort software in the system. Look for the RealPort application in installed programs list (Control Panel > Programs and Features) or check for RealPort-related processes running.
    Affected if Digi RealPort software is found installed on the system
  2. Determine installed Digi RealPort version
    Open Windows Programs and Features, locate Digi RealPort, and note the version number. Alternatively, check the version information of the RealPort executable if accessible. Compare the found version against the affected ranges: <= 1.9-40 or <= 4.8.488.0
    Affected if The installed version is 1.9-40 or earlier, or 4.8.488.0 or earlier
  3. Verify ADDP discovery service status
    Check if ADDP (Advanced Device Discovery Protocol) is enabled on the system. This may be configurable in the RealPort service settings, device network configuration, or registry entries related to device discovery services.
    Affected if ADDP discovery is enabled and listening for incoming responses
  4. Identify affected Digi hardware firmware versions
    For Digi Connectport TS/TS, Connectport LTS, Passport, CM, Portserver TS devices, check the firmware version through the device web interface, console CLI, or management software. All firmware versions are listed as affected.
    Affected if Any firmware version is running on the listed affected Digi hardware devices

A system is affected if Digi RealPort (Windows) version 1.9-40 or earlier or 4.8.488.0 or earlier is installed with ADDP enabled, or if any listed Digi hardware device firmware is running with ADDP discovery active.

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

Apply the vendor-provided patch or update Digi RealPort to a version beyond 4.8.488.0. If patching is not immediately possible, restrict network access to trusted sources and disable ADDP discovery on untrusted segments to reduce attack surface.

Fix this in Realport Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,390
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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-2021-35977 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