Description
Tavis Ormandy reported a common DNS misconfiguration that can result in a minor security issue with web
applications.
"It's a common and sensible practice to install records of the form
"localhost. IN A 127.0.0.1" into nameserver configurations, bizarrely
however, administrators often mistakenly drop the trailing dot,
introducing an interesting variation of Cross-Site Scripting (XSS) I
call Same-Site Scripting. The missing dot indicates that the record is
not fully qualified, and thus queries of the form
"localhost.example.com" are resolved. While superficially this may
appear to be harmless, it does in fact allow an attacker to cheat the
RFC2109 (HTTP State Management Mechanism) same origin restrictions, and
therefore hijack state management data."
Remediation
It is advised that non-FQ localhost entries be removed from nameserver configurations for domains that host websites that rely on HTTP state management.