# CVE-2021-23427: Arbitrary File Write via Archive Extraction (Zip Slip)

> Attackers can write arbitrary files via Zip Slip in elFinder.NetCore, potentially leading to code execution or data modification.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L/E:F/RL:U/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Sep 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-wmpm-fq7r-jq56

## What is CVE-2021-23427?

CVE-2021-23427 is a high-severity path traversal vulnerability in elFinder.NetCore, published on 1 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

This affects all versions of package elFinder.NetCore. The ExtractAsync function within the FileSystem is vulnerable to arbitrary extraction due to insufficient validation.

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

## Which versions are affected by CVE-2021-23427?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `elFinder.NetCore` | NuGet | All versions to 1.3.5 | None |
| `elFinder.NetCore` | NuGet | All versions to 1.3.5 | None |

Products: Elfinder.netcore Project Elfinder.netcore.

## How do I fix CVE-2021-23427?

No fix has been published for CVE-2021-23427 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-23427 being exploited?

There is no known exploitation of CVE-2021-23427 in the wild and no public exploit code.

## Other vulnerabilities in elFinder.NetCore

- [CVE-2021-23428](https://insights.sbomify.com/CVE-2021-23428/): Directory Traversal (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-23427 and fix it if it is affected.

What it is: CVE-2021-23427 is a high-severity path traversal vulnerability in elFinder.NetCore, published on 1 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-23427 in the wild and no public exploit code.

Affected packages and fixed versions:
- elFinder.NetCore (NuGet): affected all versions up to 1.3.5; no fix listed
- elFinder.NetCore (NuGet): affected all versions up to 1.3.5; 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/CVE-2021-23427/ (Markdown: https://insights.sbomify.com/CVE-2021-23427/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23427
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23427
- OSV: https://osv.dev/vulnerability/CVE-2021-23427

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-23427/
Summaries are generated and may contain mistakes; the official description above is the record.