CVE-2026-11771: Stack Overflow

Description

OpenVPN version 2.1.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows attackers via an off-by-one buffer write in the NTLM proxy authentication to potentially cause a crash via a crafted NTLM response from a malicious proxy server

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Weakness Type (CWE)

CWE-121 CWE-121

CWE-193 CWE-193

CWE-787 Out-of-bounds Write

References

Other References

https://community.openvpn.net/ReleaseHistory#openvpn-2621-released-1-july-2026 https://community.openvpn.net/ReleaseHistory#openvpn-275-released-1-july-2026 https://community.openvpn.net/Security%20Announcements/CVE-2026-11771

Frequently Asked Questions

What is CVE-2026-11771? +

OpenVPN version 2.1.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows attackers via an off-by-one buffer write in the NTLM proxy authentication to potentially cause a crash via a crafted NTLM response from a malicious proxy server

How do I check if I'm vulnerable to CVE-2026-11771? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-11771