What is CVE-2026-40564?

CVE-2026-40564 is a medium-severity vulnerability in Apache Flink Kubernetes Operator, classified under Files or Directories Accessible to External Parties. CVSS score: 6.5/10. Published 2026-05-26.

How severe is CVE-2026-40564?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2026-40564 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

SSRF in Apache Flink Kubernetes Operator

CVE-2026-40564

Files or Directories Accessible to External Parties, Server-Side Request Forgery (SSRF) vulnerability in Apache Flink Kubernetes Operator. The FlinkSessionJob jarURI is currently not validated so that it points to user-owned files or addresses. This lets a user with CR create permissions read files from the operator pod's filesystem and pull content from any backing store reachable through Flink's pluggable filesystem layer and access them through the submitted Flink job. Furthermore for fetching from http/https addresses there is currently no allowlist on the URI scheme, no host check, no IP-range restriction, and no protection against pointing the URI at internal or link-local addresses.This issue affects Apache Flink Kubernetes Operator: from 1.3.0 before 1.15.0. Users are recommended to upgrade to version 1.15.0, which fixes the issue.

Published 2026-05-26 · last modified 2026-07-24.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.005 (39.8th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 39.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: +0.000

Affected products

Apache Flink Kubernetes Operator
Apache Software Foundation Flink Kubernetes Operator — versions 1.3.0

Weakness classification (CWE)

Public proof-of-concept exploits

oscerd/CVE-2026-40564

References

lists.apache.org/thread/jvxs2kh2o60sl7qkl5nss4r5phzfl4cz (vendor-advisory, Mailing List)
af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2026-40564?: CVE-2026-40564 is a medium-severity vulnerability in Apache Flink Kubernetes Operator, classified under Files or Directories Accessible to External Parties. CVSS score: 6.5/10. Published 2026-05-26.
How severe is CVE-2026-40564?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2026-40564 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.