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Fencer Vulns
high 7.4

CVE-2021-3547 json

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 unr…

published 2021-07-12 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26858

cvss
7.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

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.

Patch / fix

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3547 updated

openvpn: possible certificate authentication bypass with --verify-x509-name

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.24% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD 2.0 5.8 AV:N/AC:M/Au:N/C:P/I:P/A:N

Affected products

  • n/a OpenVPN 3 Core Library

Classification

Weakness
  • CWE-305 Authentication Bypass by Primary Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.