CVE-2020-15811

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to
incorrect data validation, HTTP Request Splitting attacks may succeed
against HTTP and HTTPS traffic. This leads to cache poisoning. This allows
any client, including browser scripts, to bypass local security and poison
the browser cache and any downstream caches with content from an arbitrary
source. Squid uses a string search instead of parsing the Transfer-Encoding
header to find chunked encoding. This allows an attacker to hide a second
request inside Transfer-Encoding: it is interpreted by Squid as chunked and
split out into a second request delivered upstream. Squid will then deliver
two distinct responses to the client, corrupting any downstream caches.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=968932&gt;