# CVE-2017-15271: Use after free in n/a

> Remote attackers can cause a denial of service in PSFTPd by triggering a use-after-free via crafted SSH strings before authentication.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/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:** 15 Nov 2017
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-fcg6-9hqq-q764

## What is CVE-2017-15271?

CVE-2017-15271 is a medium-severity use after free vulnerability in n/a, published on 15 Nov 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use-after-free issue could be triggered remotely in the SFTP component of PSFTPd 10.0.4 Build 729. This issue could be triggered prior to authentication. The PSFTPd server did not automatically restart, which enabled attackers to perform a very effective DoS attack against this service. By sending a crafted SSH identification / version string to the server, a NULL pointer dereference could be caused, apparently because of a race condition in the window message handling, performing the cleanup for invalid connections. This incorrect cleanup code has a use-after-free.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2017-15271?

It affects 1 product.


Products: Psftp Psftpd.

## How do I fix CVE-2017-15271?

No fix has been published for CVE-2017-15271 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-15271 being exploited?

There is no known exploitation of CVE-2017-15271 in the wild and no public exploit code.

Public exploit code:

- PSFTPd Windows FTP Server 10.0.4 Build 729 - Log Injection / Use-After-Free (exploitdb)

## Other vulnerabilities in n/a

- [CVE-2017-15270](https://insights.sbomify.com/CVE-2017-15270/): Other in n/a (medium 5.3)
- [CVE-2017-15272](https://insights.sbomify.com/CVE-2017-15272/): Hardcoded credentials in n/a (medium 5.3)
- [CVE-2017-15269](https://insights.sbomify.com/CVE-2017-15269/): Server-side request forgery in n/a (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-15271 and fix it if it is affected.

What it is: CVE-2017-15271 is a medium-severity use after free vulnerability in n/a, published on 15 Nov 2017. 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-2017-15271 in the wild and no public exploit code.

Affected product: n/a. 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-2017-15271/ (Markdown: https://insights.sbomify.com/CVE-2017-15271/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-15271
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-15271
- OSV: https://osv.dev/vulnerability/CVE-2017-15271

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-15271/
Summaries are generated and may contain mistakes; the official description above is the record.