# CVE-2021-27649: Use after free in DiskStation Manager (DSM)

> Remote attackers can execute arbitrary code via a use-after-free flaw in the file transfer protocol component of Synology DSM.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Jun 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-59pm-73xx-3pvc

## What is CVE-2021-27649?

CVE-2021-27649 is a critical use after free vulnerability in Synology Diskstation Manager, published on 23 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Use after free vulnerability in file transfer protocol component in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via unspecified vectors.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-27649?

It affects 2 products.


Products: Synology Diskstation Manager, Synology Diskstation Manager Unified Controller.

## How do I fix CVE-2021-27649?

No fix has been published for CVE-2021-27649 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27649 being exploited?

There is no known exploitation of CVE-2021-27649 in the wild and no public exploit code.

## Other vulnerabilities in Synology Diskstation Manager

- [CVE-2022-27624](https://insights.sbomify.com/CVE-2022-27624/): Memory corruption in DiskStation Manager (DSM) (critical 10.0)
- [CVE-2022-27625](https://insights.sbomify.com/CVE-2022-27625/): Memory corruption in DiskStation Manager (DSM) (critical 10.0)
- [CVE-2022-27626](https://insights.sbomify.com/CVE-2022-27626/): Race condition in DiskStation Manager (DSM) (critical 10.0)
- [CVE-2013-6955](https://insights.sbomify.com/CVE-2013-6955/): Path traversal in n/a (critical 10.0)
- [CVE-2022-22687](https://insights.sbomify.com/CVE-2022-22687/): Memory corruption in DiskStation Manager (DSM) (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27649 and fix it if it is affected.

What it is: CVE-2021-27649 is a critical use after free vulnerability in Synology Diskstation Manager, published on 23 Jun 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-2021-27649 in the wild and no public exploit code.

Affected product: Synology Diskstation Manager. 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-2021-27649/ (Markdown: https://insights.sbomify.com/CVE-2021-27649/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27649
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27649
- OSV: https://osv.dev/vulnerability/CVE-2021-27649

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27649/
Summaries are generated and may contain mistakes; the official description above is the record.