Is CVE-2026-31838 actively exploited?

CVE-2026-31838 has no public evidence of in-the-wild exploitation as of 2026-04-07.

What is the CVSS score for CVE-2026-31838?

CVE-2026-31838 has a CVSS score of 6.9 (MEDIUM severity). Vector: 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.

How do I patch CVE-2026-31838?

Patch guidance is available from istio security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-31838.

Which products are affected by CVE-2026-31838?

3 products: istio istio, istio istio, istio istio.

CVE-2026-31838 - remediation guidance & executive summary

Description

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.

CVSS Metrics

Vector: 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
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Confidentiality: undefined
Integrity: undefined
Availability: undefined
Weaknesses: CWE-863 · Incorrect Authorization

Metadata

Primary Vendor: ISTIO
Published: 3/10/2026
Last Modified: 4/7/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

istio : istioistio : istioistio : istio

Remediation Guidance

Executive Summary

Cite this page

CVE-2026-31838. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2026-31838

View on NIST NVD

CVE-2026-31838 vulnerability