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CVE Record

CVE-2026-31837: Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails.

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.

HighCVSS 8.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Istio versions before 1.29.1, 1.28.5, and 1.27.8 can expose sensitive hardcoded default key material when JWKS retrieval is unavailable or fails. This matters because Istio often protects service-to-service authentication, so confidentiality impact can be high even without user interaction.

Executive priority

Prioritize remediation in the next urgent patch cycle for production service meshes, especially internet-facing or high-trust environments using JWT authentication.

Technical view

The flaw is in Istio's JWKS resolver failure handling. If JWKS fetching fails, affected versions may expose hardcoded defaults regardless of RequestAuthentication configuration. The CVSS 4.0 score is 8.7 with network attack vector, low complexity, no privileges, no user interaction, and high confidentiality impact.

Likely exposure

Organizations running Istio versions >=1.29.0-alpha.0 and <1.29.1, >=1.28.0-alpha.0 and <1.28.5, or <1.27.8 are potentially exposed, especially where JWT authentication depends on JWKS retrieval.

Exploitation context

The provided sources do not show CISA KEV listing or confirmed active exploitation. The risk is still material because the condition can occur remotely when JWKS resolution is unavailable or fetches fail.

Researcher notes

Evidence is limited to the advisory metadata and referenced vendor sources. The bundle identifies affected ranges, fixed versions, CWE-1392 and CWE-200, and confidentiality-focused impact, but does not provide public exploit confirmation.

Mitigation direction

  • Upgrade Istio to 1.29.1, 1.28.5, 1.27.8, or later supported releases.
  • Check Red Hat errata for affected downstream packages and supported remediation paths.
  • Prioritize meshes using RequestAuthentication or external JWKS-based JWT validation.
  • Monitor JWKS endpoint availability and resolver failures until upgrades are complete.

Validation and detection

  • Inventory Istio control plane and data plane versions across all clusters.
  • Identify RequestAuthentication resources and external JWKS dependencies.
  • Confirm deployed Istio versions meet or exceed the fixed releases.
  • Review logs or telemetry for JWKS fetch failures during the exposure window.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-1392: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · medium confidence lookup

CWE-200: Information exposure and cloud metadata lookup

Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-31837 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
8.7 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N——GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-31837Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPistio: Istio: Information disclosure and authentication bypass via JWKS resolver unavailability
other:Red Hat severity ratingcvssV3_1
  • 2026-03-10T23:02:58.238Z: Reported to Red Hat.
  • 2026-03-10T21:57:44.387Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
istioistio>= 1.29.0-alpha.0, < 1.29.1, >= 1.28.0-alpha.0, < 1.28.5, < 1.27.8Listed
Weakness

CWE details

CWE-1392CWE-200

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1392 · source CWE mapping

Use of Default Credentials

Use of Default Credentials represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-200 · source CWE mapping

Exposure of Sensitive Information to an Unauthorized Actor

Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs