# CVE-2021-21816: Information disclosure in D-LINK

> An attacker can send a crafted HTTP request to the Syslog functionality to disclose sensitive information from the device.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 16 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-c5h4-7vc8-8w5m

## What is CVE-2021-21816?

CVE-2021-21816 is a medium-severity vulnerability in D-LINK, published on 16 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An information disclosure vulnerability exists in the Syslog functionality of D-LINK DIR-3040 1.13B03. A specially crafted network request can lead to the disclosure of sensitive information. An attacker can send an HTTP request to trigger this vulnerability.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-21816?

It affects 1 product.


Products: Dlink Dir-3040 Firmware.

## How do I fix CVE-2021-21816?

No fix has been published for CVE-2021-21816 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21816 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21816 exists.

Public exploit code:

- D-Link DIR-3040 1.13B03 - Information Disclosure (nuclei): http/cves/2021/CVE-2021-21816.yaml

## Other vulnerabilities in D-LINK

- [CVE-2021-21913](https://insights.sbomify.com/CVE-2021-21913/): Hardcoded credentials in D-Link (critical 10.0)
- [CVE-2021-21820](https://insights.sbomify.com/CVE-2021-21820/): Hardcoded credentials in D-Link (critical 10.0)
- [CVE-2022-44832](https://insights.sbomify.com/CVE-2022-44832/): Command injection in n/a (critical 9.8)
- [CVE-2021-21819](https://insights.sbomify.com/CVE-2021-21819/): Command injection in D-Link (critical 9.1)
- [CVE-2023-41229](https://insights.sbomify.com/CVE-2023-41229/): D-Link DIR-3040 HTTP Request Processing Referer Heap-Based Buffer Overflow Remote Code Execution Vulnerability (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21816 and fix it if it is affected.

What it is: CVE-2021-21816 is a medium-severity vulnerability in D-LINK, published on 16 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21816 exists.

Affected product: D-LINK. 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-2021-21816/ (Markdown: https://insights.sbomify.com/CVE-2021-21816/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21816
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21816
- OSV: https://osv.dev/vulnerability/CVE-2021-21816

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21816/
Summaries are generated and may contain mistakes; the official description above is the record.