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IstioApplication

CVE-2026-31837

HIGH · 7.5 CVSS v3.1 Published 2026-03-10
Fix available
A fix is available. Upgrade to 1.27.8 / 1.28.5 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a user of Istio is impacted if the JWKS resolver becomes unavailable or the fetch fails, exposing hardcoded defaults regardless of use of the RequestAuthentication resource. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Istio prior to versions 1.29.1, 1.28.5, and 1.27.8, when the JWKS (JSON Web Key Set) resolver becomes unavailable or fails to fetch keys, the system falls back to hardcoded default values for JWT authentication. This occurs regardless of whether a RequestAuthentication resource is configured, potentially allowing unauthorized access through these hardcoded defaults.

MitigationUpgrade Istio to version 1.29.1, 1.28.5, or 1.27.8 or later to remediate the vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
IstioApplication
Affected:< 1.27.8>= 1.28.0, < 1.28.5>= 1.29.0, < 1.29.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Istio version
    Run 'istioctl version' or 'kubectl get deployment -n istio-system istiod -o jsonpath={.spec.template.spec.containers[0].image}' to get the Istio control plane version
    Affected if The version is less than 1.27.8, or between 1.28.0 and 1.28.4 inclusive, or between 1.29.0 and 1.29.0 inclusive (1.29.1 is fixed)
  2. Identify RequestAuthentication resources
    Run 'kubectl get RequestAuthentication -A -o wide' to list all RequestAuthentication resources in all namespaces
    Affected if Any RequestAuthentication resource exists that references a remote JWKS endpoint (look for 'jwksUri' field pointing to external URLs)
  3. Check for JWT authentication in AuthorizationPolicy
    Run 'kubectl get AuthorizationPolicy -A -o jsonpath={range .items[*]}{.metadata.namespace}{'\t'}{.metadata.name}{'\n'}{end}' and inspect any policies containing 'jwt' rules
    Affected if AuthorizationPolicy resources with JWT rules exist that depend on JWKS resolution
  4. Verify JWKS endpoint accessibility
    For each RequestAuthentication with a remote jwksUri, manually verify the endpoint is reachable from the istiod pod: 'kubectl exec -n istio-system deploy/istiod -- curl -s <jwksUri>'
    Affected if The JWKS endpoint returns errors, timeouts, or is unreachable from the istiod namespace

You are affected if you run an affected Istio version AND have any RequestAuthentication resources using remote JWKS endpoints that could fail, because Istio will then fall back to insecure hardcoded defaults allowing unauthorized requests.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.27.8 / 1.28.5 / 1.29.1 or later
Fixed in 1.27.81.28.51.29.1
Interim mitigation

Upgrade Istio to version 1.29.1, 1.28.5, or 1.27.8 or later to remediate the vulnerability.

Recommended fix High confidence

Upgrade to Istio 1.27.8 (if <1.27.8), 1.28.5 (if >=1.28.0 and <1.28.5), or 1.29.1 (if >=1.29.0)

  1. Identify the current Istio version running in your cluster using 'istioctl version' or checking the Istio operator/deployment manifests
  2. Determine which upgrade path applies based on your current version (see upgrade_path)
  3. Review the Istio release notes for the target version to understand any configuration or behavioral changes
  4. Create a backup of your current Istio configuration, including IstioOperator resources, gateway configs, and virtual services
  5. Upgrade Istio using 'istioctl upgrade' or your preferred installation method to reach the minimum fixed version for your branch
  6. Verify the upgrade was successful by checking 'istioctl version' and confirming all control plane and data plane components are running
  7. Test your workloads to ensure authentication and authorization policies function correctly, especially if using RequestAuthentication resources
  8. Monitor logs for any JWKS-related errors to confirm the vulnerability is remediated
Caveat Minor releases may include breaking changes; review release notes for your upgrade path and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Istio Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31837 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data