Linux Kernel OpenVPN Socket Validation Bypass

CVE-2026-80735 is a memory safety vulnerability in the Linux kernel's OpenVPN (ovpn) implementation where insufficient validation of socket ownership can lead to out-of-bounds reads. The vulnerability arises because subsystems like BPF SOCKMAP can set the sk_user_data field without properly setting the encap_type, allowing the ovpn module to dereference socket data it doesn't actually own. This affects Linux systems running OpenVPN, particularly those utilizing BPF-based networking features. An attacker with local access or ability to influence socket creation could exploit this to read sensitive kernel memory, potentially extracting cryptographic keys, authentication tokens, or other confidential data.

Casky's extended reasoning capabilities would identify this vulnerability pattern through behavioral analysis of socket handling anomalies and memory access violations. While formal MITRE ATT&CK mapping is unavailable for this specific CVE, the underlying attack pattern aligns with T1040 (Traffic Capture or Redirection) and T1557 (On-Path Interception) techniques where attackers manipulate network stack components to access sensitive data. Practitioners using Casky would observe suspicious patterns in kernel memory access logs, socket descriptor validation failures, and attempts to access socket user data without proper type verification. The platform would flag instances where socket encapsulation types are mismatched or uninitialized before dereferencing operations, enabling detection of both direct exploitation attempts and malicious BPF programs attempting to corrupt OpenVPN's socket state.