# CVE-2023-37463: Quadratic complexity bugs may lead to a denial of service

> Attackers can cause denial of service in applications using cmark-gfm by triggering quadratic complexity bugs during Markdown parsing.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Jul 2023
- **Updated:** 30 Oct 2024
- **Also known as:** DEBIAN-CVE-2023-37463, GHSA-w4qg-3vf7-m9x5, openSUSE-SU-2024:13136-1, openSUSE-SU-2026:12003-1

## What is CVE-2023-37463?

CVE-2023-37463 is a medium-severity denial of service vulnerability in github cmark-gfm, published on 13 Jul 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

cmark-gfm is an extended version of the C reference implementation of CommonMark, a rationalized version of Markdown syntax with a spec. Three polynomial time complexity issues in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. These vulnerabilities have been patched in 0.29.0.gfm.12.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2023-37463?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `python-cmarkgfm` | openSUSE:Tumbleweed | All versions | 2025.10.22-1.4 |

Products: Github Cmark-Gfm.

## How do I fix CVE-2023-37463?

Upgrade to a fixed version.

## Is CVE-2023-37463 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-37463 exists.

## Other vulnerabilities in github cmark-gfm

- [CVE-2024-22051](https://insights.sbomify.com/CVE-2024-22051/): CommonMarker Integer Overflow Vulnerability (critical 9.8)
- [CVE-2023-24824](https://insights.sbomify.com/CVE-2023-24824/): Quadratic complexity may lead to a denial of service in cmark-gfm (medium 5.3)
- [CVE-2023-26485](https://insights.sbomify.com/CVE-2023-26485/): Quadratic complexity may lead to a denial of service in cmark-gfm (medium 5.3)
- [CVE-2023-22485](https://insights.sbomify.com/CVE-2023-22485/): cmark-gfm out-of-bounds read in validate_protocol (medium 5.3)
- [CVE-2023-22486](https://insights.sbomify.com/CVE-2023-22486/): cmark-gfm Quadratic complexity bug in handle_close_bracket may lead to a denial of service (low 3.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-37463 and fix it if it is affected.

What it is: CVE-2023-37463 is a medium-severity denial of service vulnerability in github cmark-gfm, published on 13 Jul 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-37463 exists.

Affected product: github cmark-gfm. 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-2023-37463/ (Markdown: https://insights.sbomify.com/CVE-2023-37463/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-37463
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-37463
- OSV: https://osv.dev/vulnerability/CVE-2023-37463

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-37463/
Summaries are generated and may contain mistakes; the official description above is the record.