The _gnutls_x509_verify_certificate function in lib/x509/verify.c in libgnutls in GnuTLS before 2.6.1 trusts certificate chains in which the last certificate is an arbitrary trusted, self-signed certificate, which allows man-in-the-middle attackers to insert a spoofed certificate for any Distinguished Name (DN).
http://article.gmane.org/gmane.comp.encryption.gpg.gnutls.devel/3215
http://article.gmane.org/gmane.comp.encryption.gpg.gnutls.devel/3217
http://lists.opensuse.org/opensuse-security-announce/2008-12/msg00002.html
http://lists.opensuse.org/opensuse-security-announce/2009-04/msg00010.html
http://secunia.com/advisories/32619
http://secunia.com/advisories/32681
http://secunia.com/advisories/32687
http://secunia.com/advisories/32879
http://secunia.com/advisories/33501
http://secunia.com/advisories/33694
http://secunia.com/advisories/35423
http://security.gentoo.org/glsa/glsa-200901-10.xml
http://sunsolve.sun.com/search/document.do?assetkey=1-26-260528-1
http://wiki.rpath.com/Advisories:rPSA-2008-0322
http://www.debian.org/security/2009/dsa-1719
http://www.gnu.org/software/gnutls/security.html
http://www.mandriva.com/security/advisories?name=MDVSA-2008:227
http://www.redhat.com/support/errata/RHSA-2008-0982.html
http://www.securityfocus.com/archive/1/498431/100/0/threaded
http://www.securityfocus.com/bid/32232
http://www.securitytracker.com/id?1021167
http://www.ubuntu.com/usn/usn-678-2
http://www.vupen.com/english/advisories/2008/3086
http://www.vupen.com/english/advisories/2009/1567
https://exchange.xforce.ibmcloud.com/vulnerabilities/46482
https://issues.rpath.com/browse/RPL-2886
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11650
https://www.redhat.com/archives/fedora-package-announce/2008-November/msg00222.html
https://www.redhat.com/archives/fedora-package-announce/2008-November/msg00293.html