CVE-2026-40215
Description
A flaw was found in OpenVPN that occurs when a connection is being established or updated. A remote attacker could exploit this timing issue to crash the OpenVPN server, causing a temporary service disruption (Denial of Service). In some cases, it could also allow an attacker to view fragments of the server's temporary internal memory, potentially exposing sensitive data.
Statement
This Moderate impact flaw in OpenVPN is a race condition that can be remotely triggered during TLS session promotion. Successful exploitation could lead to a server crash, resulting in a denial of service, or potentially leak heap memory. The vulnerability's reliance on specific timing for the race condition to occur contributes to its Moderate severity.
Mitigation
To reduce the attack surface, restrict network access to the OpenVPN server to only trusted clients and networks. This can be achieved by configuring firewall rules to limit inbound connections to the OpenVPN port (default 1194/UDP or 443/TCP) from known, authorized sources. This operational control limits the ability of unauthorized remote attackers to attempt exploitation.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Application Data; Modify Memory; DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands
It may be possible to cause data corruption and possibly execute arbitrary code by modifying global variables or data structures at unexpected times, violating the assumptions of code that uses this global data.
Access Control
Technical Impact: Gain Privileges or Assume Identity
If a signal handler interrupts code that is executing with privileges, it may be possible that the signal handler will also be executed with elevated privileges, possibly making subsequent exploits more severe.
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