Deserialization in Feast-Dev Feast

CVE-2026-56121

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.

Vulnerability class: Insecure Deserialization

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.014 (71.6th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 72nd percentile — 71.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-56121: held from 0.014 to 0.014.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-56121?
CVE-2026-56121 is a critical-severity vulnerability in Feast-Dev Feast, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-06-24.
How severe is CVE-2026-56121?
Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-56121 known to be exploited?
3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.