# CVE-2021-34557: Memory corruption in n/a

> A buffer overflow in XScreenSaver allows attackers to bypass screen lock authentication by physically disconnecting multiple video outputs.

- **Severity:** Medium 4.6 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Jun 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-34557, GHSA-hrwv-325w-f6ch, MGASA-2021-0278, SUSE-SU-2022:2641-1, SUSE-SU-2022:2642-1, UBUNTU-CVE-2021-34557

## What is CVE-2021-34557?

CVE-2021-34557 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 10 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-34557?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `xscreensaver` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 5.44-150000.5.6.1 |
| `xscreensaver` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 5.22-8.3.1 |
| `xscreensaver` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 5.22-8.3.1 |
| `xscreensaver` | openSUSE:Leap 15.3 | All versions | 5.44-150000.5.6.1 |

Products: Fedoraproject Fedora, Xscreensaver Project Xscreensaver.

## How do I fix CVE-2021-34557?

Apply the vendor's patch.

## Is CVE-2021-34557 being exploited?

There is no known exploitation of CVE-2021-34557 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34557 and fix it if it is affected.

What it is: CVE-2021-34557 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 10 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-34557 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2021-34557/ (Markdown: https://insights.sbomify.com/CVE-2021-34557/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34557
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34557
- OSV: https://osv.dev/vulnerability/CVE-2021-34557

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34557/
Summaries are generated and may contain mistakes; the official description above is the record.