CVE-2026-56121
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 · uneditedFeast before 0.63.0 contains an unsafe deserialization vulnerability that allows unauthenticated or unauthorized attackers to achieve remote code execution by sending a crafted gRPC request to the registry server. The user_defined_function.body field of an OnDemandFeatureView spec is decoded from base64 and passed to dill.loads() before any authorization check is performed, enabling attackers to embed a malicious serialized Python object with an arbitrary __reduce__ method to execute OS commands as the feast service account.
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 confidenceFeast before 0.63.0 has an unsafe deserialization vulnerability where the user_defined_function.body field of OnDemandFeatureView specs is decoded from base64 and passed to dill.loads() before any authorization check, allowing unauthenticated attackers to achieve RCE via crafted gRPC requests to the registry server.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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 checksWork through these to decide whether this CVE applies to you.
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Check installed Feast versionRun `feast --version` or `python -c "import feast; print(feast.__version__)"` and compare the output to the affected range (versions before 0.63.0)Affected if The installed version is lower than 0.63.0
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Identify if OnDemandFeatureView with user_defined_function is definedSearch feature definition files (such as feature_repo/features.py) for OnDemandFeatureView class usage with the user_defined_function parameter set, which contains a body field that gets passed to dill.loads()Affected if OnDemandFeatureView with user_defined_function.body is defined in the feature repo
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Locate registry server configurationInspect the feature_store.yaml configuration file (typically in feature_repo/) for the registry section, noting the registry_type (should be 'grpc' or 'remote' for this vulnerability to apply)Affected if The registry is configured as a remote/grpc registry (not local)
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Check registry server network exposureReview the registry server configuration for the host/address and determine if the gRPC endpoint is exposed to untrusted networks (for example, by inspecting firewall rules, kubernetes services, or cloud security groups)Affected if The registry gRPC endpoint is accessible from untrusted network segments or the internet
You are affected if Feast version is below 0.63.0 AND the registry server is network-accessible AND OnDemandFeatureView with user_defined_function is in use, allowing unauthenticated gRPC attackers to reach the vulnerable dill.loads() call.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpgrade Feast to version 0.63.0 or later. If immediate upgrade is not feasible, restrict network access to the registry server and implement additional authentication/authorization before deserialization.
Feast 0.63.0 or later
- Check current Feast version using `pip show feast` or `feast --version`
- Upgrade Feast to version 0.63.0 or later using `pip install feast>=0.63.0`
- Verify the upgrade was successful by running `feast --version` and confirming the version is 0.63.0 or higher
- If using a requirements file, update the feast dependency to `feast>=0.63.0` and run `pip install -r requirements.txt`
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-56121 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-56121 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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