The remote host is missing an update to gnupg2 announced via advisory DSA 1141-1. Evgeny Legerov discovered that overly large comments can crash gnupg, the GNU privacy guard - a free PGP replacement, which is also present in the development branch.
For the stable distribution (sarge) this problem has been fixed in version 1.9.15-6sarge2. For the unstable distribution (sid) this problem will be fixed soon. We recommend that you upgrade your gnupg2 package. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201141-1