How severe is CVE-2026-56121?

No CVSS score has been assigned to CVE-2026-56121 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-56121?

Affected package information for CVE-2026-56121 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-56121?

Upgrade the affected component to the fixed release for CVE-2026-56121, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

How do I detect CVE-2026-56121 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2026-56121 if there is no patch (or I can't update yet)?

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.

Is CVE-2026-56121 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-56121 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-56121?

CVE-2026-56121 has an EPSS (Exploit Prediction Scoring System) score of 1.4%, placing it in the 73th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-56121?

CVE-2026-56121 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-56121 published, and has it been updated?

CVE-2026-56121 was published on June 24, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

Not in CISA KEV

CVE-2026-56121 — feast

Fix: feast-dev/feast@835cda8

CVE-2026-56121 is a Deserialization of Untrusted Data vulnerability. A fix is available — see the affected versions and patch details below.

Feast < 0.63.0 Unauthenticated RCE via ApplyFeatureView gRPC Deserialization

Published

Jun 24, 2026

Updated

Oct 28, 2026

Affected

68 versions

Patched

See advisory

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-56121.

EPSS Exploitation Probability

via FIRST.org ↗

1.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk

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

Description

Feast 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.

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-56121, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Red Hat OpenShift AI ships Feast versions affected by CVE-2026-56121. This flaw allows remote code execution only against the Feast registry gRPC server (feast serve_registry, port 6570) when that service is running and reachable. Default OpenShift AI installations are not affected. Installing OpenShift AI deploys the…

Workaround published by Red Hat

- Restrict network access to Feature Server / registry endpoints (NetworkPolicy, Route auth, no public exposure). - Do not expose the Feast registry gRPC port to untrusted networks; place behind OpenShift Route + platform authentication.

Source: Red Hat security advisory for CVE-2026-56121 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat OpenShift AI 2.25	`rhoai/odh-feature-server-rhel9:1792148523`	RHSA-2026:87410
Red Hat OpenShift AI 3.4	`rhoai/odh-pipeline-runtime-datascience-cpu-py312-rhel9:1787073866`	RHSA-2026:60520
Red Hat OpenShift AI 3.4	`rhoai/odh-feature-server-rhel9:1791863220`	RHSA-2026:84734

Frequently Asked Questions

Feast 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.

O3 Security · Impact-Aware SCA

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