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CRITICAL severity

Remote Code Execution in HalibutGHSA-hpf7-4c2g-9chf

CRITICAL

GHSA-hpf7-4c2g-9chf is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in Halibut. A fix is available for Halibut — see the affected versions and patch details below.

Also known asCVE-2021-31819
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs83th percentile — riskier than 83% of all scored CVEsHighest risk
1.36%1.86%2.36%2.85%1.9%2.4%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-hpf7-4c2g-9chf by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
.NETHalibut

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetHalibutall versions4.4.7dotnet add package Halibut --version 4.4.7

Affected Products

1 product · 1 configurations
Application
halibutoctopus
< 4.4.7
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Halibut, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update Halibut to 4.4.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hpf7-4c2g-9chf is resolved across your whole dependency graph.

  3. Workarounds

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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Remote Code Execution in Halibut (Critical 9.8)