What is CVE-2021-39156?

CVE-2021-39156 is a remotely exploitable vulnerability in Istio 1.11.0, 1.10.3 and below, and 1.9.7 and below that allows an HTTP request with a specially crafted user agent header to cause a denial of service condition.

How severe is CVE-2021-39156?

CVE-2021-39156 has a severity value of 7.5 (high).

How does CVE-2021-39156 affect Istio?

CVE-2021-39156 affects Istio versions 1.11.0, 1.10.3 and below, and 1.9.7 and below.

How can I fix CVE-2021-39156?

To fix CVE-2021-39156, it is recommended to upgrade to Istio version 1.11.1 or higher, 1.10.4 or higher, or 1.9.9 or higher, depending on the affected version.

Where can I find more information about CVE-2021-39156?

You can find more information about CVE-2021-39156 in the following references: [GitHub Advisory](https://github.com/istio/istio/security/advisories/GHSA-hqxw-mm44-gc4r) and [Istio Security Advisory](https://istio.io/latest/news/security/istio-security-2021-008).

Vulnerability/
CVE-2021-39156

high

8.1

CWE

706 863

24/8/2021

4/8/2024

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

First published: Tue Aug 24 2021(Updated: )

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.

Credit: security-advisories@github.com

Affected Software	Affected Version	How to fix
Istio Istio	<1.9.8
Istio Istio	>=1.10.0<1.10.3
Istio Istio	>=1.11.0<1.11.1

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Frequently Asked Questions

What is CVE-2021-39156?
CVE-2021-39156 is a remotely exploitable vulnerability in Istio 1.11.0, 1.10.3 and below, and 1.9.7 and below that allows an HTTP request with a specially crafted user agent header to cause a denial of service condition.
How severe is CVE-2021-39156?
CVE-2021-39156 has a severity value of 7.5 (high).
How does CVE-2021-39156 affect Istio?
CVE-2021-39156 affects Istio versions 1.11.0, 1.10.3 and below, and 1.9.7 and below.
How can I fix CVE-2021-39156?
To fix CVE-2021-39156, it is recommended to upgrade to Istio version 1.11.1 or higher, 1.10.4 or higher, or 1.9.9 or higher, depending on the affected version.
Where can I find more information about CVE-2021-39156?
You can find more information about CVE-2021-39156 in the following references: [GitHub Advisory](https://github.com/istio/istio/security/advisories/GHSA-hqxw-mm44-gc4r) and [Istio Security Advisory](https://istio.io/latest/news/security/istio-security-2021-008).

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version/istio istio/1.10.0
version/istio istio/1.11.0

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