An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Request Smuggling and Poisoning attack can succeed against the HTTP cache. The client sends an HTTP request with a Content-Length header containing "+\ "-" or an uncommon shell whitespace character prefix to the length field-value. A flaw was found in squid. A trusted client is able to perform a request smuggling and poison the HTTP cache contents with crafted HTTP(S) request messages. This attack requires an upstream server to participate in the smuggling and generate the poison response sequence. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
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