# CVE-2021-26528: Memory corruption in n/a

> Remote attackers can trigger out-of-bounds writes in Cesanta Mongoose by exhausting the memory pool, potentially leading to code execution or crashes.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** 8 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-26528, GHSA-jgrv-p7rc-9f92

## What is CVE-2021-26528?

CVE-2021-26528 is a critical memory corruption vulnerability in Cesanta Mongoose, published on 8 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The mg_http_serve_file function in Cesanta Mongoose HTTP server 7.0 is vulnerable to remote OOB write attack via connection request after exhausting memory pool.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-26528?

It affects 1 product.


Products: Cesanta Mongoose.

## How do I fix CVE-2021-26528?

Upgrade to a fixed version.

## Is CVE-2021-26528 being exploited?

There is no known exploitation of CVE-2021-26528 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-2021-26528 and fix it if it is affected.

What it is: CVE-2021-26528 is a critical memory corruption vulnerability in Cesanta Mongoose, published on 8 Feb 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-2021-26528 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-2021-26528/ (Markdown: https://insights.sbomify.com/CVE-2021-26528/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26528
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26528
- OSV: https://osv.dev/vulnerability/CVE-2021-26528

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-26528/
Summaries are generated and may contain mistakes; the official description above is the record.