Vulnerability in OpenVPN 3 Core Library (CVE-2021-3547)

Summary

Vulnerability in OpenVPN 3 Core Library (CVE-2021-3547). Confidential information can be exposed externally.

Original description

The description as published by the source.

OpenVPN 3 Core Library version 3.6 and 3.6.1 allows a man-in-the-middle attacker to bypass the certificate authentication by issuing an unrelated server certificate using the same hostname found in the verify-x509-name option in a client configuration.

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2021-3547 has been found in OpenVPN 3 Core Library.
Confidential information can be exposed externally.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "OpenVPN 3 Core Library CVE-2021-3547" on the vendor's site.

CVE-2021-3547 (OpenVPN 3 Core Library)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in OpenVPN 3 Core Library.

📍 Affected scope

Check the vendor advisory for the affected versions of OpenVPN 3 Core Library.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
Audit SBOM/dependencies for affected components.
```
資産台帳・SBOM・依存マニフェストで OpenVPN 3 Core Library を使っているサービスとバージョンを洗い出す。
2
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

References

advisory community.openvpn.net
patch community.openvpn.net