# CVE-2020-16844: Authorization bypass in Istio

> Attackers can bypass Istio authorization policies by exploiting wildcard suffix handling in DENY rules, allowing unauthorized access to protected services.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Oct 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-82mm-ffjr-h86c, RHSA-2020:3425

## What is CVE-2020-16844?

CVE-2020-16844 is a medium-severity authentication bypass vulnerability in n/a, published on 1 Oct 2020. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In Istio 1.5.0 though 1.5.8 and Istio 1.6.0 through 1.6.7, when users specify an AuthorizationPolicy resource with DENY actions using wildcard suffixes (e.g. *-some-suffix) for source principals or namespace fields, callers will never be denied access, bypassing the intended policy.

## Which versions are affected by CVE-2020-16844?

4 open source packages ship an affected version, including istio.io/istio. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `istio.io/istio` | Go | From 1.5.0 | 1.5.9 |
| `istio.io/istio` | Go | From 1.5.0 | 1.5.9 |
| `istio.io/istio` | Go | From 1.6.0 | 1.6.8 |
| `istio.io/istio` | Go | From 1.6.0 | 1.6.8 |
| `servicemesh` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-citadel` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-galley` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-istioctl` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-mixc` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-mixs` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-pilot-agent` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-pilot-discovery` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |
| `servicemesh-sidecar-injector` | Red Hat:service_mesh:1.1::el8 | All versions | 0:1.1.7-1.el8 |

Products: Istio Istio.

## How do I fix CVE-2020-16844?

Upgrade istio.io/istio to a fixed version for your release line: 1.5.9 or 1.6.8.

## Is CVE-2020-16844 being exploited?

There is no known exploitation of CVE-2020-16844 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-31921](https://insights.sbomify.com/CVE-2021-31921/): Missing authorization in n/a (critical 9.8)
- [CVE-2021-34824](https://insights.sbomify.com/CVE-2021-34824/): Information disclosure in n/a (high 8.8)
- [CVE-2026-31837](https://insights.sbomify.com/CVE-2026-31837/): Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails. (high 8.7)
- [CVE-2021-39155](https://insights.sbomify.com/CVE-2021-39155/): Authorization Policy Bypass Due to Case Insensitive Host Comparison (high 8.3)
- [CVE-2021-39156](https://insights.sbomify.com/CVE-2021-39156/): Fragments in Path May Lead to Authorization Policy Bypass (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-16844 and fix it if it is affected.

What it is: CVE-2020-16844 is a medium-severity authentication bypass vulnerability in n/a, published on 1 Oct 2020. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-16844 in the wild and no public exploit code.

Affected packages and fixed versions:
- istio.io/istio (Go): affected from 1.5.0; fixed in 1.5.9
- istio.io/istio (Go): affected from 1.5.0; fixed in 1.5.9
- istio.io/istio (Go): affected from 1.6.0; fixed in 1.6.8
- istio.io/istio (Go): affected from 1.6.0; fixed in 1.6.8

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-16844/ (Markdown: https://insights.sbomify.com/CVE-2020-16844/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-16844
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-16844
- OSV: https://osv.dev/vulnerability/CVE-2020-16844

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-16844/
Summaries are generated and may contain mistakes; the official description above is the record.