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Fencer Intel
medium 5.3

CVE-2026-31838 json

Istio HTTP debug endpoints on port 15014 to enforce namespace-based authorization, preventing cross-namespace proxy data access.

published 7mo ago modified 4mo ago also EUVD-2026-10939

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a vulnerability in Envoy RBAC header matching could allow authorization policy bypass when policies rely on HTTP headers that may contain multiple values. An attacker could craft requests with multiple header values in a way that causes Envoy to evaluate the header differently than intended, potentially bypassing authorization checks. This may allow unauthorized requests to reach protected services when policies depend on such header-based matching conditions. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.

Patch / fix

  • istio istio 1.27.8, 1.28.5, 1.29.1

Is CVE-2026-31838 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-31838 updated cvss 5.3

istio: Istio: Authorization policy bypass via Envoy RBAC header matching with multiple header values

  • Red Hat cert-manager Operator for Red Hat OpenShift cert-manager/cert-manager-operator-rhel9, cert-manager/jetstack-cert-manager-rhel9, cert-manager/cert-manager-istio-csr-rhel9, cert-manager/cert-manager-operator-bundle, cert-manager/jetstack-cert-manager-acmesolver-rhel9 Red Hat ExternalDNS Operator edo/external-dns-rhel8, edo/external-dns-rhel9 Red Hat OpenShift Service Mesh 2 openshift-service-mesh/kiali-rhel8, openshift-service-mesh/pilot-rhel8, openshift-service-mesh/proxyv2-rhel9, openshift-service-mesh/istio-cni-rhel8 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9, openshift-service-mesh/istio-cni-rhel9, openshift-service-mesh/istio-pilot-rhel9, openshift-service-mesh/istio-proxyv2-rhel9, openshift-service-mesh/istio-rhel9-operator, openshift-service-mesh/kiali-rhel9-operator, +1 more Red Hat Connectivity Link 1 rhcl-1/rhcl-rhel9-operator, rhcl-1/rhcl-operator-bundle
    affected: no fix available “Fix deferred”
  • Red Hat OpenShift Serverless openshift-serverless-1/net-istio-webhook-rhel9, openshift-serverless-1/net-istio-controller-rhel9, openshift-serverless-1/serverless-kn-operator-rhel9, openshift-serverless-1/kn-eventing-istio-controller-rhel9, openshift-serverless-1/serverless-openshift-kn-rhel9-operator Red Hat OpenShift AI (RHOAI) rhoai/odh-kserve-agent-rhel9, rhoai/odh-kserve-router-rhel9, rhoai/odh-model-registry-rhel9, rhoai/odh-model-controller-rhel8, rhoai/odh-model-controller-rhel9, rhoai/odh-kserve-controller-rhel9, +4 more
    under investigation
  • Red Hat Ansible Automation Platform 2 automation-gateway-proxy, automation-gateway-proxy-openssl30, automation-gateway-proxy-openssl32
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected products

  • istio istio

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.