# CVE-2017-2891: Use after free in Mongoose

> A use-after-free in Cesanta Mongoose allows remote code execution via a crafted HTTP POST request to a CGI target.

- **Severity:** Critical 9.8 (`CVSS:3.0/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:** Yes
- **Published:** 7 Nov 2017
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2017-2891, GHSA-rwjm-353c-64rx

## What is CVE-2017-2891?

CVE-2017-2891 is a critical use after free vulnerability in Cesanta Mongoose, published on 7 Nov 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An exploitable use-after-free vulnerability exists in the HTTP server implementation of Cesanta Mongoose 6.8. An ordinary HTTP POST request with a CGI target can cause a reuse of previously freed pointer potentially resulting in remote code execution. An attacker needs to send this HTTP request over the network to trigger this vulnerability.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2017-2891?

It affects 1 product.


Products: Cesanta Mongoose.

## How do I fix CVE-2017-2891?

Upgrade to a fixed version.

## Is CVE-2017-2891 being exploited?

There is no known exploitation of CVE-2017-2891 in the wild and no public exploit code.

## Other vulnerabilities in Cesanta Mongoose

- [CVE-2022-25299](https://insights.sbomify.com/CVE-2022-25299/): Arbitrary File Write (critical 9.8)
- [CVE-2020-25756](https://insights.sbomify.com/CVE-2020-25756/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-19307](https://insights.sbomify.com/CVE-2019-19307/): Integer overflow in n/a (critical 9.8)
- [CVE-2019-12951](https://insights.sbomify.com/CVE-2019-12951/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-20353](https://insights.sbomify.com/CVE-2018-20353/): Use after free in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-2891 and fix it if it is affected.

What it is: CVE-2017-2891 is a critical use after free vulnerability in Cesanta Mongoose, published on 7 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-2017-2891 in the wild and no public exploit code.

Affected product: Cesanta Mongoose. 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-2017-2891/ (Markdown: https://insights.sbomify.com/CVE-2017-2891/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-2891
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-2891
- OSV: https://osv.dev/vulnerability/CVE-2017-2891

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-2891/
Summaries are generated and may contain mistakes; the official description above is the record.