Server impersonation via reset certificate verification state
Published Jul 12, 2021 · Updated Aug 3, 2024
Improper certificate validation in OpenVPN 3 Core Library 3.6 and 3.6.1 allows man-in-the-middle attackers to impersonate VPN servers. The OpenSSL certificate callback's verify-x509-name handling replaces earlier certificate-check failures when the configured hostname matches. Exploitation requires network interception and a client configuration using verify-x509-name; a certificate bearing the expected hostname is then accepted despite another failed check.
Summary
What happened
Improper certificate validation in OpenVPN 3 Core Library 3.6 and 3.6.1 allows man-in-the-middle attackers to impersonate VPN servers. The OpenSSL certificate callback's verify-x509-name handling replaces earlier certificate-check failures when the configured hostname matches. Exploitation requires network interception and a client configuration using verify-x509-name; a certificate bearing the expected hostname is then accepted despite another failed check.
The record
- CVE
- CVE-2021-3547
- Published
- Jul 12, 2021
- Updated
- Aug 3, 2024
- Vendor
- OpenVPN Inc.
- Product
- OpenVPN 3 Core Library
- Classifications
- CWE-295, CWE-305, T1557
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 12, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.6 and 3.6.1
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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