# CVE-2023-4255: W3m: out-of-bounds write in function checktype() in etc.c (incomplete fix for cve-2022-38223)

> An out-of-bounds write in W3m allows attackers to cause a denial of service via a crafted HTML file.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Dec 2023
- **Updated:** 13 Feb 2025
- **Also known as:** DEBIAN-CVE-2023-4255, GHSA-hx3r-ph4g-9px9, SUSE-SU-2024:0014-1, UBUNTU-CVE-2023-4255, USN-6580-1

## What is CVE-2023-4255?

CVE-2023-4255 is a medium-severity memory corruption vulnerability in Fedoraproject Extra Packages for Enterprise Linux, published on 21 Dec 2023. 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

An out-of-bounds write issue has been discovered in the backspace handling of the checkType() function in etc.c within the W3M application. This vulnerability is triggered by supplying a specially crafted HTML file to the w3m binary. Exploitation of this flaw could lead to application crashes, resulting in a denial of service condition.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2023-4255?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `w3m` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 0.5.3.git20161120-161.9.1 |
| `w3m` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 0.5.3.git20161120-161.9.1 |

Products: Fedoraproject Extra Packages for Enterprise Linux, Fedoraproject Fedora, Tats W3m.

## How do I fix CVE-2023-4255?

Apply the vendor's patch.

## Is CVE-2023-4255 being exploited?

There is no known exploitation of CVE-2023-4255 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Extra Packages for Enterprise Linux

- [CVE-2023-34152](https://insights.sbomify.com/CVE-2023-34152/): Command injection in ImageMagick (critical 9.8)
- [CVE-2022-4170](https://insights.sbomify.com/CVE-2022-4170/): Code injection in rxvt-unicode (critical 9.8)
- [CVE-2022-40315](https://insights.sbomify.com/CVE-2022-40315/): Moodle Minor SQL injection risk in admin user browsing (critical 9.8)
- [CVE-2022-45152](https://insights.sbomify.com/CVE-2022-45152/): Moodle blind Server-Side Request Forgery (SSRF) vulnerability in LTI provider library (critical 9.1)
- [CVE-2022-24882](https://insights.sbomify.com/CVE-2022-24882/): Server side NTLM does not properly check parameters in FreeRDP (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4255 and fix it if it is affected.

What it is: CVE-2023-4255 is a medium-severity memory corruption vulnerability in Fedoraproject Extra Packages for Enterprise Linux, published on 21 Dec 2023. 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-2023-4255 in the wild and no public exploit code.

Affected product: Fedoraproject Extra Packages for Enterprise Linux. 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-2023-4255/ (Markdown: https://insights.sbomify.com/CVE-2023-4255/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4255
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4255
- OSV: https://osv.dev/vulnerability/CVE-2023-4255

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4255/
Summaries are generated and may contain mistakes; the official description above is the record.