In GNOME glib-networking through 2.64.2, the implementation of GTlsClientConnection skips hostname verification of the server's TLS certificate if the application fails to specify the expected server identity. This is in contrast to its intended documented behavior, to fail the certificate verification. Applications that fail to provide the server identity, including Balsa before 2.5.11 and 2.6.x before 2.6.1, accept a TLS certificate if the certificate is valid for any host.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-13645
• https://gitlab.gnome.org/GNOME/balsa/-/issues/34
• https://gitlab.gnome.org/GNOME/glib-networking/-/issues/135
• https://lists.fedoraproject.org/archives/list/[email protected]/message/HLEX2IP62SU6WJ4SK3U766XGLQK3J62O/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/LRCUM22YEWWKNMN2BP5LTVDM5P4VWIXS/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/TQEQJQ4XFMFCFJTEXKL2ZO3UELBPCKSK/
• https://security.gentoo.org/glsa/202007-50
• https://security.netapp.com/advisory/ntap-20200608-0004/
• https://usn.ubuntu.com/4405-1/