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HalibutApplication · Octopus

CVE-2021-31819

CRITICAL · 9.8 CVSS v3.1 Published 2021-09-22
Fix available
A fix is available. Upgrade to 4.4.7 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
In Halibut versions prior to 4.4.7 there is a deserialisation vulnerability that could allow remote code execution on systems that already trust each other based on certificate verification.

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

A deserialization vulnerability in Halibut versions prior to 4.4.7 allows remote code execution on systems that already trust each other through certificate verification. This critical flaw (CVSS 9.8) enables attackers who have achieved man-in-the-middle positioning within the trusted network to deserialize untrusted data and execute arbitrary code.

MitigationUpgrade to Halibut version 4.4.7 or later to address the deserialization vulnerability. If immediate patching is not feasible, limit network exposure and strictly enforce certificate validation to reduce the 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
HalibutApplication
Affected:< 4.4.7

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. Locate Halibut installation
    Search for halibut.exe or the Halibut binary in your environment, typically found in Octopus Deploy server or tentacle installations, or check your application's dependencies if Halibut is used as a library.
    Affected if Halibut is present in your environment
  2. Determine installed Halibut version
    Run 'halibut --version' or check the version metadata of the halibut binary/library file. If used as a .NET library, check the referenced assembly version in your project or NuGet packages.
    Affected if The version cannot be determined or is shown as an older release
  3. Compare version to 4.4.7
    Review the detected version number against the affected range. Versions prior to 4.4.7 (including 4.4.6, 4.4.0, 3.x, 2.x, etc.) are vulnerable.
    Affected if Installed version is less than 4.4.7 (e.g., 4.4.6 or earlier)
  4. Verify network trust configuration
    Examine your Halibut configuration to confirm certificate validation is enabled and identify systems that have mutual trust established for communication.
    Affected if Mutual certificate-based trust is configured between systems, as this is required for the attack to be exploitable

Your environment is affected if Halibut version is found to be less than 4.4.7 AND mutual certificate trust is established between communicating systems, allowing a man-in-the-middle attacker to deserialize malicious data.

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 4.4.7 or later
Fixed in 4.4.7
Interim mitigation

Upgrade to Halibut version 4.4.7 or later to address the deserialization vulnerability. If immediate patching is not feasible, limit network exposure and strictly enforce certificate validation to reduce the attack surface.

Recommended fix High confidence

Halibut version 4.4.7

  1. 1. Identify all systems running Halibut versions prior to 4.4.7
  2. 2. Obtain the latest Halibut version 4.4.7 or later from the official Octopus Deploy repository
  3. 3. Review release notes for any configuration or deployment changes required
  4. 4. Plan maintenance window considering the RCE risk and certificate-based trust requirements
  5. 5. Backup current Halibut configuration and deployment files
  6. 6. Upgrade Halibut on all affected systems to version 4.4.7 or later
  7. 7. Verify the upgrade was successful and Halibut services are running correctly
  8. 8. Confirm the deserialization vulnerability is no longer present
Caveat Review Octopus Deploy release notes for 4.4.7 to check for any breaking changes or deprecations

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

Fix this in Halibut Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,504.

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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-2021-31819 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