CVE-2023-26463: 
strongSwan vulnerability analysis and mitigation

CVE-2023-26463 affects strongSwan versions 5.9.8 and 5.9.9, involving a certificate verification vulnerability in TLS-based EAP methods. The vulnerability was discovered and disclosed on March 2, 2023, and affects strongSwan's implementation of certificate verification, potentially allowing remote code execution. The issue specifically impacts servers that load plugins implementing TLS-based EAP methods (EAP-TLS, EAP-TTLS, EAP-PEAP, or EAP-TNC) (Strongswan Blog).

The vulnerability stems from incorrect access control followed by an expired pointer dereference. The technical issue involves the TLS implementation in libtls incorrectly treating the public key from the peer's certificate as trusted, even when the certificate cannot be verified successfully. Additionally, the public key lacks the correct reference count, leading to a dereference of an expired pointer. The vulnerability has been assigned a CVSS v3.1 base score of 9.8 (Critical) with vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (NVD, Strongswan Blog).

The vulnerability can lead to multiple severe impacts including denial of service, information disclosure, and potential remote code execution. When exploited, it allows authentication bypass and can cause a segmentation fault. Depending on memory allocation conditions, the pointer dereference could potentially lead to code execution under an attacker's control (Strongswan Blog, NetApp Advisory).

The vulnerability is fixed in strongSwan version 5.9.10. For servers, mitigation involves ensuring they don't load plugins that implement TLS-based EAP methods (EAP-TLS, EAP-TTLS, EAP-PEAP, EAP-TNC) or not configuring them as remote authentication methods. The eap-dynamic plugin should not be used as it allows clients to select their preferred EAP method. Clients are not vulnerable if they don't load plugins for TLS-based EAP methods or don't configure such methods as their authentication method (Strongswan Blog).