# CVE-2020-26148: Use after free in n/a

> Attackers can cause a denial of service via assertion failure in the md4c library by submitting a malformed Markdown document.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-26148, GHSA-8cq8-p477-7hrv, UBUNTU-CVE-2020-26148

## What is CVE-2020-26148?

CVE-2020-26148 is a high-severity use after free vulnerability in n/a, published on 29 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

md_push_block_bytes in md4c.c in md4c 0.4.5 allows attackers to trigger use of uninitialized memory, and cause a denial of service (e.g., assertion failure) via a malformed Markdown document.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2020-26148?

It affects 1 product.


Products: Md4c Project Md4c.

## How do I fix CVE-2020-26148?

Upgrade to a fixed version.

## Is CVE-2020-26148 being exploited?

There is no known exploitation of CVE-2020-26148 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-11536](https://insights.sbomify.com/CVE-2018-11536/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-11545](https://insights.sbomify.com/CVE-2018-11545/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-11546](https://insights.sbomify.com/CVE-2018-11546/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-11547](https://insights.sbomify.com/CVE-2018-11547/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-12112](https://insights.sbomify.com/CVE-2018-12112/): Memory corruption in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26148 and fix it if it is affected.

What it is: CVE-2020-26148 is a high-severity use after free vulnerability in n/a, published on 29 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-26148 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-2020-26148/ (Markdown: https://insights.sbomify.com/CVE-2020-26148/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26148
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26148
- OSV: https://osv.dev/vulnerability/CVE-2020-26148

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26148/
Summaries are generated and may contain mistakes; the official description above is the record.