CVE-2021-39156 Fragments in Path May Lead to Authorization Policy Bypass
Attackers can bypass Istio URI path authorization policies by including fragments in HTTP requests, requiring patches to secure microservice traffic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-39156?
CVE-2021-39156 is a high-severity authentication bypass vulnerability in istio, published on 24 Aug 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Which versions are affected by CVE-2021-39156?
6 open source packages ship an affected version, including istio.io/istio. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
istio.io/istio Go | All versions | 1.9.8 |
istio.io/istio Go | All versions | 1.9.8 |
istio.io/istio Go | From 1.10.0 | 1.10.4 |
istio.io/istio Go | From 1.10.0 | 1.10.4 |
istio.io/istio Go | From 1.11.0 | 1.11.1 |
istio.io/istio Go | From 1.11.0 | 1.11.1 |
Products include Istio Istio.
How do I fix CVE-2021-39156?
Upgrade istio.io/istio to a fixed version for your release line: 1.9.8, 1.10.4 or 1.11.1.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2021-39156 being exploited?
There is no known exploitation of CVE-2021-39156 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in istio
- CVE-2021-31921 Missing authorization in n/a
- CVE-2021-34824 Information disclosure in n/a
- CVE-2026-31837 Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails.
- CVE-2021-39155 Authorization Policy Bypass Due to Case Insensitive Host Comparison
- CVE-2022-39388 Istio may allow identity impersonation if user has localhost access
Sources
Also known as GHSA-hqxw-mm44-gc4r, MINI-q55p-qmgc-gwg5, MINI-rh7w-f67j-vqv4.