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

Advisory record · `GHSA-q63x-9pfm-mjx4`

- **Identifiers:** `GHSA-q63x-9pfm-mjx4` · `CVE-2026-56121`
- **State:** Confirmed
- **Severity:** CVSS 9.3 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-502](https://cwe.mitre.org/data/definitions/502.html)
- **Tags:** [Insecure deserialization](https://agentprime.io/advisories/tag/deserialization.md)
- **Published:** 24 Jun 2026
- **Updated:** 3 Nov 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 24 Jun 2026, 18:32 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.3: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `feast` (PyPI): affected `<0.63.0`; fixed in `0.63.0`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.3 Critical, CVSS 4.0: `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`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.014, the 72nd percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 24 Jun 2026, 14:49 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-56121)
- 24 Jun 2026, 18:32 UTC: [Confirmed by GitHub Advisory Database](https://github.com/advisories/GHSA-q63x-9pfm-mjx4)
- 3 Nov 2026, 21:31 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-q63x-9pfm-mjx4)

## Sources

- [GitHub Advisory Database: GHSA-q63x-9pfm-mjx4](https://github.com/advisories/GHSA-q63x-9pfm-mjx4)
- [OSV: GHSA-q63x-9pfm-mjx4](https://osv.dev/vulnerability/GHSA-q63x-9pfm-mjx4)
- <https://nvd.nist.gov/vuln/detail/CVE-2026-56121>
- <https://github.com/feast-dev/feast/commit/835cda8e2c1359f1f496ad72701dbd6a73bdb25a>
- <https://access.redhat.com/errata/RHSA-2026:60520>
- <https://access.redhat.com/security/cve/CVE-2026-56121>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2492229>
- <https://github.com/feast-dev/feast>
- <https://github.com/feast-dev/feast/releases/tag/v0.63.0>
- <https://huntr.com/bounties/d64b8111-180b-46ba-afa3-c877fda2ede6>
- <https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-56121.json>
- <https://www.vulncheck.com/advisories/feast-unauthenticated-rce-via-applyfeatureview-grpc-deserialization>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-q63x-9pfm-mjx4>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-q63x-9pfm-mjx4/>. Everything for agents: <https://agentprime.io/llms.txt>.