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TI-2021-11909 Aliases CVE-2021-31921GHSA-3j84-jghj-gqwg

Istio before 1.8.6 and 1.9.x before 1.9.5 contains a remotely exploitable vulnerability…

Priority MEDIUM 45CWE-862Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-862.

Summary

Istio before 1.8.6 and 1.9.x before 1.9.5 contains a remotely exploitable vulnerability where an external client can access unexpected services in the cluster, bypassing authorization checks, when a gateway is configured with AUTO_PASSTHROUGH routing configuration.

Why it matters now

EPSS 0.01454 73rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed Red Hat: 2 advisories

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
——all versions—No fix listedCNA
  • — Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:*before 1.8.6; 1.9.0 to before 1.9.5Vulnerableistio
  • cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:* Versions before 1.8.6; 1.9.0 to before 1.9.5 Vulnerable ·istio

Remediation

Red Hat 2 advisories

  • RHSA-2021:2085 Released 2021-05-20 · Red Hat rating Important
    servicemesh security update
    • OpenShift Service Mesh 1.1 servicemesh-1.1.15-4.el8, servicemesh-citadel-1.1.15-4.el8, servicemesh-galley-1.1.15-4.el8 +6
  • RHSA-2021:2061 Released 2021-05-20 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 2.0.5 security update
    • OpenShift Service Mesh 2.0 servicemesh-2.0.5-3.el8, servicemesh-istioctl-2.0.5-3.el8, servicemesh-mixc-2.0.5-3.el8 +3

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift Service Mesh 1.1Fixed RHSA-2021:2085
OpenShift Service Mesh 2.0Fixed RHSA-2021:2061

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-31921
  2. 2026-10-03 Alias added: GHSA-3j84-jghj-gqwg

References

Exploit 1

  • TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2022-06055 Authorization Policy bypass in Istio CVSS 3.1CRITICAL 9.8
  • TI-2026-24390 Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails. CVSS 4.0HIGH 8.7
  • TI-2022-13090 Ill-formed headers may lead to unexpected behavior in Istio CVSS 3.1CRITICAL 9.8
  • TI-2022-18654 Istio vulnerable to denial of service attack due to Golang Regex Library CVSS 3.1HIGH 7.5
See all 28 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences