CVE-2026-39312 Pre-Auth EAP-TLS DoS on SoftEther VPN Developer Edition
An unauthenticated remote attacker can crash the SoftEther VPN server by sending a malformed EAP-TLS packet, disrupting all active sessions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-39312?
CVE-2026-39312 is a high-severity denial of service vulnerability in SoftEtherVPN, published on 7 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
SoftEtherVPN is a an open-source cross-platform multi-protocol VPN Program. In 5.2.5188 and earlier, a pre-authentication denial-of-service vulnerability exists in SoftEther VPN Developer Edition 5.2.5188 (and likely earlier versions of Developer Edition). An unauthenticated remote attacker can crash the vpnserver process by sending a single malformed EAP-TLS packet over raw L2TP (UDP/1701), terminating all active VPN sessions.
Weakness: CWE-789
Which versions are affected by CVE-2026-39312?
It affects 1 product.
Products include Softether Softethervpn.
How do I fix CVE-2026-39312?
No fix has been published for CVE-2026-39312 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-39312 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39312 exists.
Sources
Also known as GHSA-q5g3-qhc6-pr3h.