# CVE-2018-20356: Use after free in n/a

> A use-after-free flaw in the Mongoose embedded web server library allows attackers to cause a crash or execute arbitrary code.

- **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:** No
- **Published:** 10 Jun 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-2hwq-hrjc-wwr4

## What is CVE-2018-20356?

CVE-2018-20356 is a critical use after free vulnerability in Cesanta Mongoose, published on 10 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An invalid read of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in mongoose.c in Cesanta Mongoose Embedded Web Server Library 6.13 and earlier allows a denial of service (application crash) or remote code execution.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2018-20356?

It affects 1 product.


Products: Cesanta Mongoose.

## How do I fix CVE-2018-20356?

No fix has been published for CVE-2018-20356 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-20356 being exploited?

There is no known exploitation of CVE-2018-20356 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-2018-20356 and fix it if it is affected.

What it is: CVE-2018-20356 is a critical use after free vulnerability in Cesanta Mongoose, published on 10 Jun 2019. 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-2018-20356 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-2018-20356/ (Markdown: https://insights.sbomify.com/CVE-2018-20356/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20356
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20356
- OSV: https://osv.dev/vulnerability/CVE-2018-20356

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20356/
Summaries are generated and may contain mistakes; the official description above is the record.