CVE-2018-6459

Vulnerability

In strongSwan 5.6.1, the rsa_pss_params_parse function in libstrongswan/credentials/keys/signature_params.c does not properly handle ASN.1 encoded RSASSA-PSS signature parameters that omit the mask generation function (MGF) parameter. When parsing such a crafted signature, an undefined stack read occurs, leading to a potential crash. This affects signatures in certificates and IKEv2 signature authentication (RFC 7427) [1].

Exploitation

An attacker sends a crafted RSASSA-PSS signature value (e.g., in a certificate or an IKEv2 authentication exchange) that lacks the MGF parameter. No prior authentication or special network position is required; the attacker merely needs to deliver the malformed input to a strongSwan 5.6.1 system [1].

Impact

Successful exploitation causes a denial-of-service crash of the strongSwan process. Remote code execution is not possible [1]. The crash may disrupt IPsec VPN services or other IKE-based communications.

Mitigation

strongSwan 5.6.2, released on February 19, 2018, fixes the vulnerability. A patch is also available for 5.6.1 [1]. Gentoo users should upgrade to >=net-vpn/strongswan-5.7.1 [2]. No workaround exists for unpatched installations.