Kevin Wojtysiak discovered a vulnerability in strongSwan, an IPsec based VPN solution.
When using the OpenSSL plugin for ECDSA based authentication, an empty, zeroed or otherwise invalid signature is handled as a legitimate one. An attacker could use a forged signature to authenticate like a legitimate user and gain access to the VPN (and everything protected by this).
While the issue looks like CVE-2012-2388 (RSA signature based authentication bypass), it is unrelated.
For the stable distribution (squeeze), this problem has been fixed in version 4.4.1-5.3.
For the testing distribution (wheezy), this problem has been fixed in version 4.5.2-1.5+deb7u1.
For the unstable distribution (sid), this problem has been fixed in version 4.6.4-7.
We recommend that you upgrade your strongswan packages.