CVE-2026-31837: Istio JWKS resolver failure exposes hardcoded default keys

CVE-2026-31837 · Severity: high · CVSS 7.5 · Published 2026-03-10

Istio is an open-source platform used to manage and secure communication between microservices in cloud environments. A security flaw has been identified where the system may fail to properly validate security tokens if its internal resolver service becomes unavailable. This could allow an attacker to bypass intended security policies and access sensitive information by relying on hardcoded default settings that should not be exposed.

Technologies: Istio. Vendors: Istio.

Quick answers

Is CVE-2026-31837 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31837 being exploited in the wild.
How severe is CVE-2026-31837?
High severity, with a CVSS score of 7.5, published 10 March 2026.
Which products and versions are affected?
Istio < 1.27.8, >= 1.28.0-alpha.0, < 1.28.5, >= 1.29.0-alpha.0, < 1.29.1.
Is there a fix for CVE-2026-31837?
A patch was published on 2026-03-10: Fixes released in versions 1.29.1, 1.28.5, and 1.27.8 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-31837 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-31837?
Check whether you run Istio at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A vulnerability exists in Istio's authentication mechanism where a failure in the JSON Web Key Set (JWKS) resolver leads to the exposure of hardcoded default keys. This occurs if the resolver becomes unavailable or a fetch operation fails, causing the system to fall back to these defaults regardless of the RequestAuthentication resource configuration. An unauthenticated remote attacker can exploit this behavior to bypass security controls and gain unauthorized access to sensitive information (CWE-200). The issue is rooted in improper handling of resolver failures and the use of default credentials (CWE-1392). Patches are available in versions 1.29.1, 1.28.5, and 1.27.8.

Affected products

  • Istio Istio < 1.27.8, >= 1.28.0-alpha.0, < 1.28.5, >= 1.29.0-alpha.0, < 1.29.1
  • Red Hat Red Hat OpenShift AI 2.25
  • Red Hat Red Hat OpenShift Service Mesh 3.0, 3.1, 3.2

Timeline

  • 2026-03-10: disclosed: Initial advisory published by Istio and GitHub
  • 2026-03-10: patched: Fixes released in versions 1.29.1, 1.28.5, and 1.27.8
  • 2026-04-23: advisory: Red Hat issued security advisory RHSA-2026:10184 for OpenShift AI

References

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