SB2026090525 - Multiple vulnerabilities in OpenVPN Server
Published: September 5, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 7 vulnerabilities.
1) Resource exhaustion (CVE-ID: CVE-2026-84732)
CWE-ID: CWE-400 - Resource exhaustion
CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in the reliability layer when handling TLS timeouts and acknowledgements. A remote attacker can send acknowledgements for packets that cannot be outstanding to cause a denial of service.
2) OS Command Injection (CVE-ID: CVE-2026-84256)
CWE-ID: CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
CVSSv4: 1.8 [CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause command-line misbehavior.
The vulnerability exists due to improper neutralization of special characters in CreateProcess() command-line quoting when processing characters that are special to cmd.exe. A remote attacker can provide specially crafted command-line content to cause command-line misbehavior.
Exploitation requires a validation script and a rogue CA.
3) Untrusted search path (CVE-ID: CVE-2026-84226)
CWE-ID: CWE-426 - Untrusted Search Path
CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a local user to cause OpenVPN to invoke an unintended executable.
The vulnerability exists due to an untrusted search path in tapctl when invoking netsh.exe. A local user can influence executable resolution to cause OpenVPN to invoke an unintended executable.
4) Incorrect permission assignment for critical resource (CVE-ID: CVE-2026-82312)
CWE-ID: CWE-732 - Incorrect Permission Assignment for Critical Resource
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 cause a denial of service.
The vulnerability exists due to incorrect permission assignment for critical resources in the Windows service exit event and netsh.exe guard semaphore when OpenVPN creates system objects with a NULL DACL. A local user can block the netsh semaphore or send events to cause a denial of service.
Only setups not using the interactive service, or using the automatic service to start or stop OpenVPN, are affected.
5) Out-of-bounds read (CVE-ID: CVE-2026-78221)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to an out-of-bounds read in openvpnserv when processing NRPT domains with UTF-8-encoded IDN domains. A remote attacker can supply UTF-8-encoded IDN domains to disclose sensitive information.
6) Path traversal (CVE-ID: CVE-2026-78043)
CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a local user to cause OpenVPN to start a user-controlled configuration file.
The vulnerability exists due to path traversal in openvpnserv configuration-path validation when processing config paths containing \'/\'. A local user can provide a config path containing \'/\' to cause OpenVPN to start a user-controlled configuration file.
Windows path-validation APIs do not treat \'/\' as a path separator, while file-opening APIs do.
7) Off-by-one (CVE-ID: CVE-2026-81738)
CWE-ID: CWE-193 - Off-by-one Error
CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a single-byte buffer overflow.
The vulnerability exists due to an off-by-one error in the write_dhcp_search_str() temporary-buffer guard when processing DHCP options. A remote attacker can supply suitable DHCP options to cause a single-byte buffer overflow.
Remediation
Install update from vendor's website.