# GHSA-wx77-rp39-c6vg: Regular Expression Denial of Service in markdown

> Attackers can cause denial of service by submitting long strings with underscores to the markdown parser, affecting applications using this library.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Sep 2020

## What is GHSA-wx77-rp39-c6vg?

GHSA-wx77-rp39-c6vg is a denial of service vulnerability in markdown, published on 4 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

All versions of `markdown` are vulnerable to Regular Expression Denial of Service (ReDoS). The `markdown.toHTML()` function has significantly degraded performance when parsing long strings containing underscores. This may lead to Denial of Service if the parser accepts user input.

## Recommendation

No fix is currently available. Consider using an alternative package until a fix is made available.

## Which versions are affected by GHSA-wx77-rp39-c6vg?

2 open source packages ship an affected version, including markdown.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `markdown` | npm | From 0.0.0 | None |
| `markdown` | npm | From 0.0.0 | None |

## How do I fix GHSA-wx77-rp39-c6vg?

No fix has been published for GHSA-wx77-rp39-c6vg yet. Limit exposure of the affected software until one is available.

## Is GHSA-wx77-rp39-c6vg being exploited?

There is no known exploitation of GHSA-wx77-rp39-c6vg in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-wx77-rp39-c6vg and fix it if it is affected.

What it is: GHSA-wx77-rp39-c6vg is a denial of service vulnerability in markdown, published on 4 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 GHSA-wx77-rp39-c6vg in the wild and no public exploit code.

Affected packages and fixed versions:
- markdown (npm): affected from 0.0.0; no fix listed
- markdown (npm): affected from 0.0.0; no fix listed

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/GHSA-wx77-rp39-c6vg/ (Markdown: https://insights.sbomify.com/GHSA-wx77-rp39-c6vg/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-wx77-rp39-c6vg

---
From sbomify Insights: https://insights.sbomify.com/GHSA-wx77-rp39-c6vg/
Summaries are generated and may contain mistakes; the official description above is the record.