CVE-2021-3547

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.

Published: 2021-07-12 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3547 is rated Moderate Risk (50.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.97%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-3547

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.97% +0.93%
2 2025-12-03 0.11% 0.04% -0.07%
3 2025-11-07 — 0.11% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3547

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.4 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 5.2 [email protected]
5.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 4.9 [email protected]

Weakness enumeration for CVE-2021-3547

OS Trackers for CVE-2021-3547

vendor priority summary link
debian unimportant CVE-2021-3547 unimportant priority: Debian including 1 source packages (openvpn3-client), 3 status rows across 3 suites (forky, sid, trixie): resolved 3. https://security-tracker.debian.org/tracker/CVE-2021-3547
suse high CVE-2021-3547 severity important: SUSE including 3 source package names (openvpn, openvpn-auth-pam-plugin, openvpn-devel), 93 product×package rows across 47 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (47 product lines)): Known Not Affected 93. https://www.suse.com/security/cve/CVE-2021-3547/

Affected software / configurations for CVE-2021-3547

Vendor Product Version Raw CPE
openvpn openvpn 3.6 cpe:2.3:a:openvpn:openvpn:3.6:*:*:*:*:*:*:*
openvpn openvpn 3.6.1 cpe:2.3:a:openvpn:openvpn:3.6.1:*:*:*:*:*:*:*

References for CVE-2021-3547

cvelogic Threat Intelligence