# CVE-2018-20450: Use after free in n/a

> Attackers can cause a denial of service via a crafted file due to a double free vulnerability in the libxls library.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/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:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Dec 2018
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2018-20450, GHSA-r369-mhv6-47fj, UBUNTU-CVE-2018-20450

## What is CVE-2018-20450?

CVE-2018-20450 is a medium-severity use after free vulnerability in n/a, published on 25 Dec 2018. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The read_MSAT function in ole.c in libxls 1.4.0 has a double free that allows attackers to cause a denial of service (application crash) via a crafted file, a different vulnerability than CVE-2017-2897.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2018-20450?

It affects 1 product.


Products: Libxls Project Libxls.

## How do I fix CVE-2018-20450?

Upgrade to a fixed version.

## Is CVE-2018-20450 being exploited?

There is no known exploitation of CVE-2018-20450 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2017-2910](https://insights.sbomify.com/CVE-2017-2910/): Memory corruption in libxls (high 8.8)
- [CVE-2018-20452](https://insights.sbomify.com/CVE-2018-20452/): Use after free in n/a (high 8.8)
- [CVE-2017-12108](https://insights.sbomify.com/CVE-2017-12108/): Integer overflow in libxls (high 8.8)
- [CVE-2017-12109](https://insights.sbomify.com/CVE-2017-12109/): Integer overflow in libxls (high 8.8)
- [CVE-2017-12110](https://insights.sbomify.com/CVE-2017-12110/): Integer overflow in libxls (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-20450 and fix it if it is affected.

What it is: CVE-2018-20450 is a medium-severity use after free vulnerability in n/a, published on 25 Dec 2018. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2018-20450 in the wild and no public exploit code.

Affected product: n/a. 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-2018-20450/ (Markdown: https://insights.sbomify.com/CVE-2018-20450/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20450
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20450
- OSV: https://osv.dev/vulnerability/CVE-2018-20450

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20450/
Summaries are generated and may contain mistakes; the official description above is the record.