# CVE-2021-32840: Path Traversal in SharpZipLib

> Attackers can extract malicious TAR files to write arbitrary files outside the target directory, potentially leading to code execution.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Jan 2022
- **Updated:** 22 Apr 2025
- **Also known as:** GHSA-m22m-h4rf-pwq3, UBUNTU-CVE-2021-32840

## What is CVE-2021-32840?

CVE-2021-32840 is a high-severity path traversal vulnerability in icsharpcode sharpziplib, published on 26 Jan 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

SharpZipLib (or #ziplib) is a Zip, GZip, Tar and BZip2 library. Prior to version 1.3.3, a TAR file entry `../evil.txt` may be extracted in the parent directory of `destFolder`. This leads to arbitrary file write that may lead to code execution. The vulnerability was patched in version 1.3.3.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2021-32840?

2 open source packages ship an affected version, including SharpZipLib. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `SharpZipLib` | NuGet | All versions | 1.3.3 |
| `SharpZipLib` | NuGet | All versions | 1.3.3 |

Products: Sharpziplib Project Sharpziplib.

## How do I fix CVE-2021-32840?

Upgrade SharpZipLib to 1.3.3 or later.

## Is CVE-2021-32840 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-32840 exists.

## Other vulnerabilities in icsharpcode sharpziplib

- [CVE-2018-1002208](https://insights.sbomify.com/CVE-2018-1002208/): Improper Limitation of a Pathname to a Restricted Directory in SharpZipLib (medium 5.5)
- [CVE-2021-32841](https://insights.sbomify.com/CVE-2021-32841/): Path Traversal in SharpZipLib (medium 4.0)
- [CVE-2021-32842](https://insights.sbomify.com/CVE-2021-32842/): Path Traversal in SharpZipLib (medium 4.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32840 and fix it if it is affected.

What it is: CVE-2021-32840 is a high-severity path traversal vulnerability in icsharpcode sharpziplib, published on 26 Jan 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-32840 exists.

Affected packages and fixed versions:
- SharpZipLib (NuGet): affected all versions; fixed in 1.3.3
- SharpZipLib (NuGet): affected all versions; fixed in 1.3.3

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-2021-32840/ (Markdown: https://insights.sbomify.com/CVE-2021-32840/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32840
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32840
- OSV: https://osv.dev/vulnerability/CVE-2021-32840

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32840/
Summaries are generated and may contain mistakes; the official description above is the record.