# CVE-2023-20191: Auth bypass in Cisco IOS XR Software

> Unauthenticated remote attackers can bypass configured Access Control Lists on MPLS interfaces in Cisco IOS XR Software.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Sep 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-5hxg-4c73-j4wf

## What is CVE-2023-20191?

CVE-2023-20191 is a medium-severity authentication bypass vulnerability in Cisco Ios Xr, published on 13 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the access control list (ACL) processing on MPLS interfaces in the ingress direction of Cisco IOS XR Software could allow an unauthenticated, remote attacker to bypass a configured ACL.

 This vulnerability is due to incomplete support for this feature. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass an ACL on the affected device.

   There are workarounds that address this vulnerability.

   

 
 This advisory is part of the September 2023 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2023 Semiannual Cisco IOS XR Software Security Advisory Bundled Publication .

Weakness: CWE-863 (Incorrect Authorization), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2023-20191?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2023-20191?

No fix has been published for CVE-2023-20191 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-20191 being exploited?

There is no known exploitation of CVE-2023-20191 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xr

- [CVE-2020-3118](https://insights.sbomify.com/CVE-2020-3118/): Cisco IOS XR Software Discovery Protocol Format String (high 8.8, exploited in the wild)
- [CVE-2020-3569](https://insights.sbomify.com/CVE-2020-3569/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2020-3566](https://insights.sbomify.com/CVE-2020-3566/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2010-3035](https://insights.sbomify.com/CVE-2010-3035/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (high 7.5, exploited in the wild)
- [CVE-2022-20821](https://insights.sbomify.com/CVE-2022-20821/): Cisco IOS XR Open Port (medium 6.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-20191 and fix it if it is affected.

What it is: CVE-2023-20191 is a medium-severity authentication bypass vulnerability in Cisco Ios Xr, published on 13 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-20191 in the wild and no public exploit code.

Affected product: Cisco Ios Xr. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2023-20191/ (Markdown: https://insights.sbomify.com/CVE-2023-20191/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-20191
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-20191
- OSV: https://osv.dev/vulnerability/CVE-2023-20191

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-20191/
Summaries are generated and may contain mistakes; the official description above is the record.