# CVE-2021-28838: Null dereference in n/a

> A null pointer dereference in the httpd binary of various D-Link access points allows remote attackers to cause a denial of service via crafted network packets.

- **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:** 10 Aug 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-qg9w-6w4c-q3pf

## What is CVE-2021-28838?

CVE-2021-28838 is a high-severity vulnerability in n/a, published on 10 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Null pointer dereference vulnerability in D-Link DAP-2310 2,10RC039, DAP-2330 1.10RC036 BETA, DAP-2360 2.10RC055, DAP-2553 3.10rc039 BETA, DAP-2660 1.15rc131b, DAP-2690 3.20RC115 BETA, DAP-2695 1.20RC093, DAP-3320 1.05RC027 BETA and DAP-3662 1.05rc069 in the sbin/httpd binary. The crash happens at the `atoi' operation when a specific network package are sent to the httpd binary.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-28838?

It affects 9 products.


Products: Dlink Dap-2310 Firmware, Dlink Dap-2330 Firmware, Dlink Dap-2360 Firmware, Dlink Dap-2553 Firmware, Dlink Dap-2660 Firmware, Dlink Dap-2690 Firmware, Dlink Dap-2695 Firmware, Dlink Dap-3320 Firmware, Dlink Dap-3662 Firmware.

## How do I fix CVE-2021-28838?

No fix has been published for CVE-2021-28838 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-28838 being exploited?

There is no known exploitation of CVE-2021-28838 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-38873](https://insights.sbomify.com/CVE-2022-38873/): Denial of service in n/a (high 7.5)
- [CVE-2021-28839](https://insights.sbomify.com/CVE-2021-28839/): Null dereference in n/a (high 7.5)
- [CVE-2021-28840](https://insights.sbomify.com/CVE-2021-28840/): Null dereference in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28838 and fix it if it is affected.

What it is: CVE-2021-28838 is a high-severity vulnerability in n/a, published on 10 Aug 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-2021-28838 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-2021-28838/ (Markdown: https://insights.sbomify.com/CVE-2021-28838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28838
- OSV: https://osv.dev/vulnerability/CVE-2021-28838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28838/
Summaries are generated and may contain mistakes; the official description above is the record.