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SYNTHESIS OF THE VULNERABILITY

An attacker can use HTTP Chunked data, in order to bypass the
"RequestHeader unset" directive of Apache httpd mod_headers.

– Impacted products: Apache httpd
– Severity: 2/4
– Creation date: 01/04/2014

DESCRIPTION OF THE VULNERABILITY

The HTTP Transfer-Encoding header can use the "chunked" type, to
indicate that data is split in chunks before being transmitted.

The "RequestHeader unset Abc" directive of the mod_headers module
of Apache httpd indicates to remove the HTTP Abc header. However,
if an attacker puts the HTTP Abc header in a chunked part,
mod_headers does not remove it.

An attacker can therefore use HTTP Chunked data, in order to
bypass the "RequestHeader unset" directive of Apache httpd
mod_headers.

ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN

http://vigilance.fr/vulnerability/Apache-httpd-bypassing-mod-headers-unset-14503