# CVE-2021-26843: Denial of service in n/a

> A crafted HTTP GET request can crash the sthttpd daemon due to overlapping memory ranges in the de_dotdot function, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/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:** 7 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-67j3-q5rv-5gjr

## What is CVE-2021-26843?

CVE-2021-26843 is a high-severity denial of service vulnerability in n/a, published on 7 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in sthttpd through 2.27.1. On systems where the strcpy function is implemented with memcpy, the de_dotdot function may cause a Denial-of-Service (daemon crash) due to overlapping memory ranges being passed to memcpy. This can triggered with an HTTP GET request for a crafted filename. NOTE: this is similar to CVE-2017-10671, but occurs in a different part of the de_dotdot function.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2021-26843?

It affects 1 product.


Products: Sthttpd Project Sthttpd.

## How do I fix CVE-2021-26843?

No fix has been published for CVE-2021-26843 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-26843 being exploited?

There is no known exploitation of CVE-2021-26843 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2017-10671](https://insights.sbomify.com/CVE-2017-10671/): Memory corruption in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-26843 and fix it if it is affected.

What it is: CVE-2021-26843 is a high-severity denial of service vulnerability in n/a, published on 7 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-2021-26843 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-2021-26843/ (Markdown: https://insights.sbomify.com/CVE-2021-26843/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26843
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26843
- OSV: https://osv.dev/vulnerability/CVE-2021-26843

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-26843/
Summaries are generated and may contain mistakes; the official description above is the record.