# CVE-2005-2531: Denial of service in n/a

> Remote attackers can cause client disconnections in OpenVPN servers configured with verb 0 and no TLS authentication by triggering certificate authentication failures.

- **Severity:** Medium 5.0 (`AV:N/AC:L/Au:N/C:N/I:N/A:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2005
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2005-2531, GHSA-h572-qc5h-fc64

## What is CVE-2005-2531?

CVE-2005-2531 is a medium-severity denial of service vulnerability in n/a, published on 24 Aug 2005. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

OpenVPN before 2.0.1, when running with "verb 0" and without TLS authentication, does not properly flush the OpenSSL error queue when a client fails certificate authentication to the server and causes the error to be processed by the wrong client, which allows remote attackers to cause a denial of service (client disconnection) via a large number of failed authentication attempts.

## Which versions are affected by CVE-2005-2531?

It affects 1 product.


Products: Openvpn Openvpn.

## How do I fix CVE-2005-2531?

Upgrade to a fixed version.

## Is CVE-2005-2531 being exploited?

There is no known exploitation of CVE-2005-2531 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2025-12106](https://insights.sbomify.com/CVE-2025-12106/): Memory corruption in OpenVPN (critical 9.1)
- [CVE-2024-5594](https://insights.sbomify.com/CVE-2024-5594/): Information disclosure in OpenVPN (critical 9.1)
- [CVE-2018-7544](https://insights.sbomify.com/CVE-2018-7544/): Cross-site request forgery in n/a (critical 9.1)
- [CVE-2006-1629](https://insights.sbomify.com/CVE-2006-1629/): Code injection in n/a (critical 9.0)
- [CVE-2024-4877](https://insights.sbomify.com/CVE-2024-4877/): Privilege escalation in OpenVPN (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2005-2531 and fix it if it is affected.

What it is: CVE-2005-2531 is a medium-severity denial of service vulnerability in n/a, published on 24 Aug 2005. 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-2005-2531 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-2005-2531/ (Markdown: https://insights.sbomify.com/CVE-2005-2531/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2005-2531
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2005-2531
- OSV: https://osv.dev/vulnerability/CVE-2005-2531

---
From sbomify Insights: https://insights.sbomify.com/CVE-2005-2531/
Summaries are generated and may contain mistakes; the official description above is the record.