# CVE-2017-12164: Auth bypass in gdm

> Attackers can bypass screen lock and gain user access if autologin is enabled, due to a missing state check in GDM.

- **Severity:** Medium 4.1 (`CVSS:3.0/AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Jul 2018
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2017-12164, GHSA-87vr-968r-r3qp, MGASA-2018-0056

## What is CVE-2017-12164?

CVE-2017-12164 is a medium-severity authentication bypass vulnerability in GNOME gdm, published on 26 Jul 2018. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A flaw was discovered in gdm 3.24.1 where gdm greeter was no longer setting the ran_once boolean during autologin. If autologin was enabled for a victim, an attacker could simply select 'login as another user' to unlock their screen.

Weakness: CWE-665 (Improper Initialization), CWE-592 (DEPRECATED: Authentication Bypass Issues)

## Which versions are affected by CVE-2017-12164?

It affects 1 product.


Products: Gnome Gnome Display Manager.

## How do I fix CVE-2017-12164?

Apply the vendor's patch.

## Is CVE-2017-12164 being exploited?

There is no known exploitation of CVE-2017-12164 in the wild and no public exploit code.

## Other vulnerabilities in GNOME gdm

- [CVE-2018-14424](https://insights.sbomify.com/CVE-2018-14424/): Use after free in n/a (high 7.8)
- [CVE-2020-16125](https://insights.sbomify.com/CVE-2020-16125/): gdm3 would start gnome-initial-setup if it cannot contact accountservice (high 7.2)
- [CVE-2013-4169](https://insights.sbomify.com/CVE-2013-4169/): Path traversal in n/a (medium 6.9)
- [CVE-2020-27837](https://insights.sbomify.com/CVE-2020-27837/): Race condition in gdm (medium 6.4)
- [CVE-2013-7273](https://insights.sbomify.com/CVE-2013-7273/): Denial of service in n/a (low 2.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-12164 and fix it if it is affected.

What it is: CVE-2017-12164 is a medium-severity authentication bypass vulnerability in GNOME gdm, published on 26 Jul 2018. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2017-12164 in the wild and no public exploit code.

Affected product: GNOME gdm. 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-2017-12164/ (Markdown: https://insights.sbomify.com/CVE-2017-12164/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-12164
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-12164
- OSV: https://osv.dev/vulnerability/CVE-2017-12164

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-12164/
Summaries are generated and may contain mistakes; the official description above is the record.