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Tectia ClientApplication · Ssh

CVE-2021-27891

HIGH · 8.8 CVSS v3.1 Published 2021-03-15
Fix available
A fix is available. Upgrade to 6.4.19 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable 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
SSH Tectia Client and Server before 6.4.19 on Windows have weak key generation. ConnectSecure on Windows is affected.

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

SSH Tectia Client and Server before version 6.4.19 on Windows, as well as ConnectSecure on Windows, use weak cryptographic key generation. This vulnerability could allow an attacker to compromise SSH communications by exploiting keys generated with insufficient entropy or predictable generation methods.

MitigationUpgrade SSH Tectia Client/Server and ConnectSecure to version 6.4.19 or later on all Windows systems. Verify that newly generated SSH keys meet current cryptographic standards after the upgrade.

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
Tectia ClientApplication
Affected:< 6.4.19
Tectia ConnectsecureApplication
Affected:all versions
Tectia ServerApplication
Affected:< 6.4.19

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

CVSS:3.1/AV:N/AC:L/PR:L/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 installed SSH Tectia product
    Locate SSH Tectia installation on the Windows system by checking Program Files or using the system's installed programs list. Determine whether SSH Tectia Client, Server, or ConnectSecure is present.
    Affected if Any of the three products (Client, Server, or ConnectSecure) is installed on Windows
  2. Check installed version number
    Using the product's built-in about or version information feature, or by inspecting the installed software details, obtain the exact version number of the SSH Tectia product.
    Affected if The version is less than 6.4.19 for Client or Server, or if ConnectSecure is present at any version (all versions are affected)
  3. Identify existing SSH host keys
    Locate SSH host key files in the product's configuration directory. These are typically stored in locations such as /etc/ssh, the product's config folder, or user-specific directories depending on the installation.
    Affected if Host keys exist and were generated by a version prior to 6.4.19 or by any version of ConnectSecure
  4. Identify user-generated SSH keys
    Search for SSH private key files in user home directories, particularly in .ssh folders or the product's key storage location. Examine key file creation timestamps if available.
    Affected if User keys exist and were generated using the vulnerable key generation method prior to upgrading to 6.4.19 or later

A user is affected if SSH Tectia Client or Server is installed at a version below 6.4.19, or if ConnectSecure is present at any version, and weak cryptographic keys generated by these versions are still in use.

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 6.4.19 or later
Fixed in 6.4.19
Interim mitigation

Upgrade SSH Tectia Client/Server and ConnectSecure to version 6.4.19 or later on all Windows systems. Verify that newly generated SSH keys meet current cryptographic standards after the upgrade.

Recommended fix Moderate confidence

6.4.19 for Tectia Client and Server

  1. 1. Identify the installed Tectia product(s) on Windows systems (Client, Server, or ConnectSecure)
  2. 2. For Tectia Client: upgrade to version 6.4.19 or later
  3. 3. For Tectia Server: upgrade to version 6.4.19 or later
  4. 4. For Tectia ConnectSecure: note that all versions are affected per the advisory; contact SSH.com for specific patch availability
  5. 5. After upgrading, regenerate any SSH keys that were generated using the vulnerable key generation on affected systems
  6. 6. Distribute new public keys to authorized servers/clients as needed
Caveat Review release notes for 6.4.19 for any configuration or compatibility changes before upgrading

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

Fix this in Tectia Client Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

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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-2021-27891 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