# CVE-2023-40546: Shim: out-of-bounds read printing error messages

> A flaw in Shim causes a crash when printing error messages due to mismatched parameters, leading to denial of service during variable creation failures.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/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:** 29 Jan 2024
- **Updated:** 20 Nov 2025
- **Also known as:** AZL-33984, AZL-34157, AZL-35253, AZL-35261, AZL-35271, BELL-CVE-2023-40546, DEBIAN-CVE-2023-40546, GHSA-9fh5-955w-9jfh, OESA-2023-1800, OESA-2023-1801, OESA-2023-1838, UBUNTU-CVE-2023-40546

## What is CVE-2023-40546?

CVE-2023-40546 is a medium-severity vulnerability in Fedoraproject Fedora, published on 29 Jan 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in Shim when an error happened while creating a new ESL variable. If Shim fails to create the new variable, it tries to print an error message to the user; however, the number of parameters used by the logging function doesn't match the format string used by it, leading to a crash under certain circumstances.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2023-40546?

It affects 3 products.


Products: Fedoraproject Fedora, Redhat Enterprise Linux, Redhat Shim.

## How do I fix CVE-2023-40546?

Apply the vendor's patch.

## Is CVE-2023-40546 being exploited?

There is no known exploitation of CVE-2023-40546 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-2023-40546 and fix it if it is affected.

What it is: CVE-2023-40546 is a medium-severity vulnerability in Fedoraproject Fedora, published on 29 Jan 2024. 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-2023-40546 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-2023-40546/ (Markdown: https://insights.sbomify.com/CVE-2023-40546/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-40546
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-40546
- OSV: https://osv.dev/vulnerability/CVE-2023-40546

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-40546/
Summaries are generated and may contain mistakes; the official description above is the record.