ID CVE-2007-0086
Summary ** DISPUTED ** The Apache HTTP Server, when accessed through a TCP connection with a large window size, allows remote attackers to cause a denial of service (network bandwidth consumption) via a Range header that specifies multiple copies of the same fragment. NOTE: the severity of this issue has been disputed by third parties, who state that the large window size required by the attack is not normally supported or configured by the server, or that a DDoS-style attack would accomplish the same goal.
Vulnerable Configurations
  • cpe:2.3:a:apache:http_server:-:*:*:*:*:*:*:*
Base: 7.8 (as of 21-04-2021 - 14:46)
  • XML Entity Expansion
    An attacker submits an XML document to a target application where the XML document uses nested entity expansion to produce an excessively large output XML. XML allows the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
  • Regular Expression Exponential Blowup
    An adversary may execute an attack on a program that uses a poor Regular Expression(Regex) implementation by choosing input that results in an extreme situation for the Regex. A typical extreme situation operates at exponential time compared to the input size. This is due to most implementations using a Nondeterministic Finite Automaton(NFA) state machine to be built by the Regex algorithm since NFA allows backtracking and thus more complex regular expressions. The algorithm builds a finite state machine and based on the input transitions through all the states until the end of the input is reached. NFA engines may evaluate each character in the input string multiple times during the backtracking. The algorithm tries each path through the NFA one by one until a match is found; the malicious input is crafted so every path is tried which results in a failure. Exploitation of the Regex results in programs hanging or taking a very long time to complete. These attacks may target various layers of the Internet due to regular expressions being used in validation.
  • XML Ping of the Death
    An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
cvss-vector via4 AV:N/AC:L/Au:N/C:N/I:N/A:C
refmap via4
  • 20070103 a cheesy Apache / IIS DoS vuln (+a question)
  • 20070104 Re: a cheesy Apache / IIS DoS vuln (+a question)
osvdb 33456
statements via4
contributor Mark J Cox
lastmodified 2007-01-11
organization Red Hat
statement Red Hat does not consider this issue to be a security vulnerability. The pottential attacker has to send acknowledgement packets periodically to make server generate traffic. Exactly the same effect could be achieved by simply downloading the file. The statement that setting the TCP window size to arbitrarily high value would permit the attacker to disconnect and stop sending ACKs is false, because Red Hat Enterprise Linux limits the size of the TCP send buffer to 4MB by default.
Last major update 21-04-2021 - 14:46
Published 05-01-2007 - 18:28
Last modified 21-04-2021 - 14:46
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