Feast vulnerable to unsafe deserialization RCE in registry server via UDF proto

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-56121: 1.41% estimated exploitation activity in the next 30 days; percentile 72.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

24 Jun 2026, 18:32 UTC

Last modified by the source

3 Nov 2026, 21:31 UTC

Source last checked

4 Nov 2026, 06:20 UTC

1. Revision 2 · amended · 4 Nov 2026

   Amended from osv record GHSA-q63x-9pfm-mjx4

2. Revision 1 · created · 3 Nov 2026

   Published from ghsa record GHSA-q63x-9pfm-mjx4

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# Patch Next advisory brief: CVE-2026-56121

Advisory: Feast vulnerable to unsafe deserialization RCE in registry server via UDF proto
IDs: CVE-2026-56121, GHSA-q63x-9pfm-mjx4
Record: https://patchnext.com/advisories/cve-2026-56121 (revision 2, source checked 4 Nov 2026, 06:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: feast 0.63.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI feast: affected < 0.63.0; fixed in 0.63.0

## Suggested inspection (read-only)
- `python -m pip show feast`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on feast.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-q63x-9pfm-mjx4 (GitHub-reviewed advisory GHSA-q63x-9pfm-mjx4 lists affected ranges: PyPI feast >=0 <0.63.0)
- Verified: https://osv.dev/vulnerability/GHSA-q63x-9pfm-mjx4 (OSV record GHSA-q63x-9pfm-mjx4 lists affected ranges: PyPI feast >=0 <0.63.0 (fixed))

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