GHSA-7226-c5q3-mc6p
Severity by source
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable authenticated race condition (PR:L, AC:H); server crash is primary impact (A:H) with minor freed-memory read exposure (C:L); no integrity or scope change.
AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
Primary rating from Vendor (CNA).
CVSS VectorVendor
Lifecycle Timeline
5Description PRE-NVD
AnalysisAI
Use-after-free in OpenVPN's ack_write_buf() function allows an authenticated network client to crash the VPN server or potentially read freed heap memory by delivering a precisely-timed sequence of control channel and authentication packets. Affected releases span the 2.6.x and 2.7.x branches, with fixes shipping in v2.6.21 and v2.7.5 on July 1, 2026. No public exploit code or CISA KEV listing has been identified at time of analysis, and the AC:H/PR:L requirements materially limit realistic exploitation.
Technical ContextAI
OpenVPN's control channel handles key exchange, session negotiation, and acknowledgment buffering between peers. The vulnerability resides in ack_write_buf(), the function responsible for queuing acknowledgment packets within the control channel. A use-after-free (CWE-416 per description - though the NVD-assigned CWE is CWE-125, Out-of-bounds Read, likely reflecting the memory-read aspect of freed heap access) occurs when a race condition between the arrival of control channel packets and authentication packets causes ack_write_buf() to operate on already-freed memory. This freed-memory access can produce reads of stale heap content (explaining VC:L in the CVSS 4.0 vector) and, more reliably, corrupts process state leading to a server crash (VA:H). The bug was independently discovered by three researchers - 章鱼哥, Haiyang Huang, and Haruki Oyama - a convergence that suggests the code path is reachable via standard client behavior rather than requiring obscure protocol manipulation.
RemediationAI
Upgrade to OpenVPN v2.7.5 (2.7.x users) or v2.6.21 (2.6.x users), both released July 1, 2026 and available at https://github.com/OpenVPN/openvpn/releases/tag/v2.7.5 and documented at https://community.openvpn.net/Security%20Announcements/CVE-2026-12996. Ubuntu system administrators should apply USN-8540-1 via standard package management. If immediate patching is operationally blocked, the most effective compensating control is to restrict which authenticated identities can reach the OpenVPN control channel - for example, enforcing strict certificate pinning and revoking certificates for any untrusted or external clients, reducing the population of principals capable of triggering the race. Rate-limiting or connection throttling at the network edge will not prevent exploitation since the timing window is within a single session, not across many connections. No configuration knob disables ack_write_buf() independently. These workarounds are partial mitigations only; patching remains the definitive fix.
A cross-protocol scripting issue was discovered in the management interface in OpenVPN through 2.4.5. Rated critical sev
OpenVPN version 2.3.12 and newer is vulnerable to unauthenticated Denial of Service of server via received large control
openvpnserv.exe (aka the interactive service helper) in OpenVPN 2.4.x before 2.4.6 allows a local attacker to cause a do
Use after free in OpenVPN version 2.6.0 to 2.6.6 may lead to undefined behavoir, leaking memory buffers or remote execut
Comodo Dome Firewall 2.7.0 contains a reflected cross-site scripting vulnerability that allows attackers to inject malic
Comodo Dome Firewall 2.7.0 contains multiple reflected cross-site scripting vulnerabilities in the openvpn_users endpoin
OpenVPN versions before 2.3.3 and 2.4.x before 2.4.4 are vulnerable to a buffer overflow vulnerability when key-method 1
OpenVPN plug-ins on Windows with OpenVPN 2.6.9 and earlier could be loaded from any directory, which allows an attacker
OpenVPN 2.1 until v2.4.12 and v2.5.6 may enable authentication bypass in external authentication plug-ins when more than
The Aviatrix OpenVPN client through 2.5.7 on Linux, macOS, and Windows is vulnerable when OpenSSL parameters are altered
Insufficient argument validation in OpenVPN 2.7_alpha1 through 2.7_rc1 allows an attacker to trigger a heap buffer over-
OpenVPN version 2.4.0 through 2.6.10 on Windows allows an external, lesser privileged process to create a named pipe whi
Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
View allVendor StatusVendor
SUSE
Severity: Moderate| Product | Status |
|---|---|
| SUSE Linux Enterprise Desktop 15 SP7 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Server 16.0 | Affected |
| SUSE Linux Enterprise Server 16.1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Affected |
| openSUSE Leap 16.0 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP5 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP4 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP5 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP6 | Affected |
| SUSE Linux Enterprise Server 12 SP5 | Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS Extended Security | Affected |
| SUSE Linux Enterprise Server 15 SP4 | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5 | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6 | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Manager Proxy 4.3 | Affected |
| SUSE Manager Proxy LTS 4.3 | Affected |
| SUSE Manager Retail Branch Server 4.3 | Affected |
| SUSE Manager Retail Branch Server LTS 4.3 | Affected |
| SUSE Manager Server 4.3 | Affected |
| SUSE Manager Server LTS 4.3 | Affected |
| SUSE CaaS Platform 4.0 | Affected |
| SUSE Enterprise Storage 6 | Affected |
| SUSE Enterprise Storage 7 | Affected |
| SUSE Enterprise Storage 7.1 | Affected |
| SUSE Linux Enterprise Desktop 12 | Affected |
| SUSE Linux Enterprise Desktop 12 SP1 | Affected |
| SUSE Linux Enterprise Desktop 12 SP2 | Affected |
| SUSE Linux Enterprise Desktop 12 SP3 | Affected |
| SUSE Linux Enterprise Desktop 12 SP4 | Affected |
| SUSE Linux Enterprise Desktop 15 | Affected |
| SUSE Linux Enterprise Desktop 15 SP1 | Affected |
| SUSE Linux Enterprise Desktop 15 SP2 | Affected |
| SUSE Linux Enterprise Desktop 15 SP3 | Affected |
| SUSE Linux Enterprise Desktop 15 SP4 | Affected |
| SUSE Linux Enterprise Desktop 15 SP5 | Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP1 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP2 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP3 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP4 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Affected |
| SUSE Linux Enterprise High Performance Computing 15-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15-LTSS | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP1 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP2 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP3 | Affected |
| SUSE Linux Enterprise Point of Sale 12 SP2-CLIENT | Affected |
| SUSE Linux Enterprise Real Time 15 SP2 | Affected |
| SUSE Linux Enterprise Real Time 15 SP3 | Affected |
| SUSE Linux Enterprise Real Time 15 SP4 | Affected |
| SUSE Linux Enterprise Server 12 | Affected |
| SUSE Linux Enterprise Server 12 SP1 | Affected |
| SUSE Linux Enterprise Server 12 SP1-LTSS | Affected |
| SUSE Linux Enterprise Server 12 SP2 | Affected |
| SUSE Linux Enterprise Server 12 SP2-BCL | Affected |
| SUSE Linux Enterprise Server 12 SP2-ESPOS | Affected |
| SUSE Linux Enterprise Server 12 SP2-LTSS | Affected |
| SUSE Linux Enterprise Server 12 SP3 | Affected |
| SUSE Linux Enterprise Server 12 SP3-BCL | Affected |
| SUSE Linux Enterprise Server 12 SP3-ESPOS | Affected |
| SUSE Linux Enterprise Server 12 SP3-LTSS | Affected |
| SUSE Linux Enterprise Server 12 SP4 | Affected |
| SUSE Linux Enterprise Server 12 SP4-ESPOS | Affected |
| SUSE Linux Enterprise Server 12 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 12-LTSS | Affected |
| SUSE Linux Enterprise Server 15 | Affected |
| SUSE Linux Enterprise Server 15 SP1 | Affected |
| SUSE Linux Enterprise Server 15 SP1-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP2 | Affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP3 | Affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | Affected |
| SUSE Linux Enterprise Server 15-LTSS | Affected |
| SUSE Linux Enterprise Server for Raspberry Pi 12 SP2 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP2 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP3 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Affected |
| SUSE Manager Proxy 4.0 | Affected |
| SUSE Manager Proxy 4.1 | Affected |
| SUSE Manager Proxy 4.2 | Affected |
| SUSE Manager Retail Branch Server 4.0 | Affected |
| SUSE Manager Retail Branch Server 4.1 | Affected |
| SUSE Manager Retail Branch Server 4.2 | Affected |
| SUSE Manager Server 4.0 | Affected |
| SUSE Manager Server 4.1 | Affected |
| SUSE Manager Server 4.2 | Affected |
| SUSE OpenStack Cloud 7 | Affected |
| SUSE OpenStack Cloud 8 | Affected |
| SUSE OpenStack Cloud 9 | Affected |
| SUSE OpenStack Cloud Crowbar 8 | Affected |
| SUSE OpenStack Cloud Crowbar 9 | Affected |
| openSUSE Leap 15.3 | Affected |
| openSUSE Leap 15.4 | Affected |
| openSUSE Leap 15.5 | Affected |
| openSUSE Leap 15.6 | Affected |
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-51239