# CVE-2021-29488: Creation of files outside the Download Folder through malicious PAR2 files

> Attackers can write files outside the configured download directory using malicious PAR2 files, potentially overwriting system files.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N`)
- **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:** 7 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-29488, UBUNTU-CVE-2021-29488

## What is CVE-2021-29488?

CVE-2021-29488 is a medium-severity path traversal vulnerability in sabnzbd, published on 7 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

SABnzbd is an open source binary newsreader. A vulnerability was discovered in SABnzbd that could trick the `filesystem.renamer()` function into writing downloaded files outside the configured Download Folder via malicious PAR2 files. A patch was released as part of SABnzbd 3.2.1RC1. As a workaround, limit downloads to NZBs without PAR2 files, deny write permissions to the SABnzbd process outside areas it must access to perform its job, or update to a fixed version.

Weakness: CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2021-29488?

It affects 1 product.


Products: Sabnzbd Sabnzbd.

## How do I fix CVE-2021-29488?

Upgrade to a fixed version.

## Is CVE-2021-29488 being exploited?

There is no known exploitation of CVE-2021-29488 in the wild and no public exploit code.

## Other vulnerabilities in sabnzbd

- [CVE-2020-13124](https://insights.sbomify.com/CVE-2020-13124/): Command injection in n/a (high 8.8)
- [CVE-2023-34237](https://insights.sbomify.com/CVE-2023-34237/): Remote code execution via specially crafted script settings in SABnzbd (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-29488 and fix it if it is affected.

What it is: CVE-2021-29488 is a medium-severity path traversal vulnerability in sabnzbd, published on 7 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-29488 in the wild and no public exploit code.

Affected product: sabnzbd. 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-2021-29488/ (Markdown: https://insights.sbomify.com/CVE-2021-29488/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29488
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29488
- OSV: https://osv.dev/vulnerability/CVE-2021-29488

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-29488/
Summaries are generated and may contain mistakes; the official description above is the record.