# CVE-2020-18780: Use after free in n/a

> Attackers can cause a denial of service in the NASM assembler by providing a crafted command that triggers a use-after-free error.

- **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:** 22 Aug 2023
- **Updated:** 4 Oct 2024
- **Also known as:** DEBIAN-CVE-2020-18780, GHSA-32c4-v26c-m9ch, UBUNTU-CVE-2020-18780

## What is CVE-2020-18780?

CVE-2020-18780 is a medium-severity use after free vulnerability in Nasm Netwide Assembler, published on 22 Aug 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

A Use After Free vulnerability in function new_Token in asm/preproc.c in nasm 2.14.02 allows attackers to cause a denial of service via crafted nasm command.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-18780?

It affects 1 product.


Products: Nasm Netwide Assembler.

## How do I fix CVE-2020-18780?

Upgrade to a fixed version.

## Is CVE-2020-18780 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-18780 exists.

## Other vulnerabilities in Nasm Netwide Assembler

- [CVE-2004-1287](https://insights.sbomify.com/CVE-2004-1287/): Memory corruption in n/a (critical 10.0)
- [CVE-2020-24978](https://insights.sbomify.com/CVE-2020-24978/): Use after free in n/a (critical 9.8)
- [CVE-2008-7177](https://insights.sbomify.com/CVE-2008-7177/): Memory corruption in n/a (critical 9.3)
- [CVE-2023-31722](https://insights.sbomify.com/CVE-2023-31722/): Memory corruption in n/a (high 7.8)
- [CVE-2022-44370](https://insights.sbomify.com/CVE-2022-44370/): Memory corruption in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-18780 and fix it if it is affected.

What it is: CVE-2020-18780 is a medium-severity use after free vulnerability in Nasm Netwide Assembler, published on 22 Aug 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-18780 exists.

Affected product: Nasm Netwide Assembler. 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-2020-18780/ (Markdown: https://insights.sbomify.com/CVE-2020-18780/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-18780
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-18780
- OSV: https://osv.dev/vulnerability/CVE-2020-18780

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-18780/
Summaries are generated and may contain mistakes; the official description above is the record.