Red Hat Bugzilla – Bug 1353760
CVE-2016-1000104 mod_fcgid: mod_fcgid sets environmental variable based on user supplied Proxy request header
Last modified: 2016-07-19 03:16:36 EDT
Dominic Scheirlinck of VendHQ reports: Many software projects and vendors have implemented support for the “Proxy” request header in their respective CGI implementations and languages by creating the “HTTP_PROXY” environmental variable based on the header value. When this variable is used (in many cases automatically by various HTTP client libraries) any outgoing requests generated in turn from the attackers original request can be redirected to an attacker controlled proxy. This allows attackers to view potentially sensitive information, reply with malformed data, or to hold connections open causing a potential denial of service. The mod_fcgi module provides support for CGI. If passed a “Proxy” header in the request mod_cgi will automatically populate the HTTP_PROXY environmental variable with whatever user supplied value is present.
Acknowledgments: Name: Scott Geary (VendHQ)
Statement: This issue is addressed through the Apache HTTPD update for CVE-2016-5387 which prevent the Proxy header from automatically being converted into the HTTP_PROXY environmental variable. Unless the "FcgidPassHeader Proxy" is used mod_fcgid is not vulnerable to this attack when used with updated HTTPD. This issue is not currently planned to be addressed in future updates. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.