CVE-2026-40557

CVE-2026-40557 is a medium-severity security vulnerability in org.apache.storm:storm-metrics-prometheus (maven), affecting versions >= 2.6.3, < 2.8.7. It is fixed in 2.8.7.

Summary

Improper Certificate Validation via Global SSL Context Downgrade in Apache Storm Prometheus Reporter

Versions Affected: from 2.6.3 to 2.8.6

Description: 

In production deployments where an administrator enables storm.daemon.metrics.reporter.plugin.prometheus.skip_tls_validation (by default it is disabled) intending to affect only the Prometheus reporter, the undocumented global side effect creates an attack surface across every TLS-protected communication channel in the Storm daemon.

The PrometheusPreparableReporter class implements an INSECURE_TRUST_MANAGER that accepts all SSL certificates without validation, with empty checkClientTrusted and checkServerTrusted methods. Most critically, when the storm.daemon.metrics.reporter.plugin.prometheus.skip_tls_validation configuration option is enabled (default = disabled) for HTTPS Prometheus PushGateway connections, the INSECURE_CONNECTION_FACTORY calls SSLContext.setDefault(sslContext), which globally replaces the JVM's default SSL context rather than applying the insecure context only to the Prometheus connection. This payload flows through storm.yaml configuration → PrometheusPreparableReporter.prepare() → INSECURE_CONNECTION_FACTORY → SSLContext.setDefault(), resulting in a JVM-wide TLS security downgrade. All subsequent HTTPS connections in the process - including ZooKeeper, Thrift, Netty, and UI connections - silently trust all certificates, including self-signed, expired, and attacker-generated ones, enabling man-in-the-middle interception of cluster state, topology submissions, tuple data, and administrative credentials.

Mitigation: 2.x users should upgrade to 2.8.7 if the Prometheus Metrics Reporter is used. Prometheus Metrics Reporter Users who cannot upgrade immediately should remove the storm.daemon.metrics.reporter.plugin.prometheus.skip_tls_validation: true setting from their storm.yaml configuration and instead configure a proper truststore containing the PushGateway's certificate.

Impact

CVE-2026-40557 has a CVSS score of 4.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.8.7); upgrading removes the vulnerable code path.

Affected versions

org.apache.storm:storm-metrics-prometheus (>= 2.6.3, < 2.8.7)

Security releases

org.apache.storm:storm-metrics-prometheus → 2.8.7 (maven)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade org.apache.storm:storm-metrics-prometheus to 2.8.7 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

  1. What is CVE-2026-40557? CVE-2026-40557 is a medium-severity security vulnerability in org.apache.storm:storm-metrics-prometheus (maven), affecting versions >= 2.6.3, < 2.8.7. It is fixed in 2.8.7.
  2. How severe is CVE-2026-40557? CVE-2026-40557 has a CVSS score of 4.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
  3. Which versions of org.apache.storm:storm-metrics-prometheus are affected by CVE-2026-40557? org.apache.storm:storm-metrics-prometheus (maven) versions >= 2.6.3, < 2.8.7 is affected.
  4. Is there a fix for CVE-2026-40557? Yes. CVE-2026-40557 is fixed in 2.8.7. Upgrade to this version or later.
  5. Is CVE-2026-40557 exploitable, and should I be worried? Whether CVE-2026-40557 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  6. What actually determines whether CVE-2026-40557 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  7. How do I fix CVE-2026-40557? Upgrade org.apache.storm:storm-metrics-prometheus to 2.8.7 or later.

Other vulnerabilities in org.apache.storm:storm-metrics-prometheus

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