# GHSA-wm7q-rxch-43mx: Byass due to validation before canonicalization in serve

> Attackers can bypass file ignore rules to access restricted files or directory listings via URL encoding.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Sep 2020

## What is GHSA-wm7q-rxch-43mx?

GHSA-wm7q-rxch-43mx is a path traversal vulnerability in serve, published on 1 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Versions of `serve` before 6.5.2 are vulnerable to the bypass of the ignore functionality. The bypass is possible because validation happens before canonicalization of paths and filenames.

Example:
Here we have a server that ignores the file test.txt.
```
const serve = require('serve')
const server = serve(__dirname, {
      port: 1337,
      ignore: ['test.txt']
})
```

Using the URL encoded form of a letter (%65 instead of e) attacker can bypass the ignore control accessing the file. 

`curl http://localhost:1337/t%65st.txt`

Additionally this technique can be used to get directory listings of ignored directories.

## Recommendation

Update to version 6.5.2 or later.

## Which versions are affected by GHSA-wm7q-rxch-43mx?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `serve` | npm | All versions | 6.5.2 |
| `serve` | npm | All versions | 6.5.2 |

## How do I fix GHSA-wm7q-rxch-43mx?

Upgrade serve to 6.5.2 or later.

## Is GHSA-wm7q-rxch-43mx being exploited?

There is no known exploitation of GHSA-wm7q-rxch-43mx in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-wm7q-rxch-43mx and fix it if it is affected.

What it is: GHSA-wm7q-rxch-43mx is a path traversal vulnerability in serve, published on 1 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-wm7q-rxch-43mx in the wild and no public exploit code.

Affected packages and fixed versions:
- serve (npm): affected all versions; fixed in 6.5.2
- serve (npm): affected all versions; fixed in 6.5.2

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-wm7q-rxch-43mx/ (Markdown: https://insights.sbomify.com/GHSA-wm7q-rxch-43mx/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-wm7q-rxch-43mx

---
From sbomify Insights: https://insights.sbomify.com/GHSA-wm7q-rxch-43mx/
Summaries are generated and may contain mistakes; the official description above is the record.