SB2026102737 - Multiple vulnerabilities in OpenVPN

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Main Vulnerability Database SB2026102737

SB2026102737 - Multiple vulnerabilities in OpenVPN

Published: October 27, 2026

Security Bulletin ID SB2026102737
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 3
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

Medium 33% Low 67%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 3 vulnerabilities.


1) Improper Check for Unusual or Exceptional Conditions (CVE-ID: N/A)

CWE-ID: CWE-754 - Improper Check for Unusual or Exceptional Conditions

CVSSv4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to disrupt an OpenVPN client's operation.

The vulnerability exists due to improper handling of missing key material in the OpenVPN tls-crypt-v2 handshake when attempting to add a wrapped client key without available key material. A remote attacker can operate a malicious server that triggers this client-side error to prevent the client from working properly.


2) Improper Neutralization of Null Byte or NUL Character (CVE-ID: CVE-2026-84790)

CWE-ID: CWE-158 - Improper Neutralization of Null Byte or NUL Character

CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to potentially bypass intended certificate subject validation.

The vulnerability exists due to improper handling of null bytes in OpenVPN certificate subject validation when processing certificates containing embedded null bytes. A remote attacker can present a specially crafted certificate subject to potentially cause inconsistent interpretation of its contents and bypass intended certificate subject checks.

mbedTLS builds already reject certificates containing null bytes.


3) Integer underflow (CVE-ID: CVE-2026-88964)

CWE-ID: CWE-191 - Integer underflow

CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]


The vulnerability allows a local user to potentially cause a denial of service.

The vulnerability exists due to an unsigned integer underflow in OpenVPN option handling when clearing domain_search_list. A local user can trigger the affected clearing operation to potentially disrupt processing through an incorrectly wrapped unsigned value.


Remediation

Install update from vendor's website.

References