Vulnerability Mapping:
ALLOWEDThis CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review (with careful review of mapping notes) Abstraction: ClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
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Description
The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is "asymmetric."
Extended Description
This can lead to poor performance due to "amplification" of resource consumption, typically in a non-linear fashion. This situation is worsened if the product allows malicious users or attackers to consume more resources than their access level permits.
Common Consequences
This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Sometimes this is a factor in "flood" attacks, but other types of amplification exist.
High
Potential Mitigations
Phase: Architecture and Design
An application must make resources available to a client commensurate with the client's access level.
Phase: Architecture and Design
An application must, at all times, keep track of allocated resources and meter their usage appropriately.
Phase: System Configuration
Consider disabling resource-intensive algorithms on the server side, such as Diffie-Hellman key exchange.
Effectiveness: High
Note: Business requirements may prevent disabling resource-intensive algorithms.
Relationships
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
Nature
Type
ID
Name
ChildOf
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase
Note
Architecture and Design
Implementation
Operation
Applicable Platforms
This listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages
Class: Not Language-Specific (Undetermined Prevalence)
Operating Systems
Class: Not OS-Specific (Undetermined Prevalence)
Architectures
Class: Not Architecture-Specific (Undetermined Prevalence)
Technologies
Class: Not Technology-Specific (Undetermined Prevalence)
Class: Client Server (Undetermined Prevalence)
Demonstrative Examples
Example 1
This code listens on a port for DNS requests and sends the result to the requesting address.
(bad code)
Example Language: Python
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.bind( (UDP_IP,UDP_PORT) ) while true:
data = sock.recvfrom(1024) if not data:
break
(requestIP, nameToResolve) = parseUDPpacket(data) record = resolveName(nameToResolve) sendResponse(requestIP,record)
This code sends a DNS record to a requesting IP address. UDP allows the source IP address to be easily changed ('spoofed'), thus allowing an attacker to redirect responses to a target, which may be then be overwhelmed by the network traffic.
Example 2
This function prints the contents of a specified file requested by a user.
(bad code)
Example Language: PHP
function printFile($username,$filename){
//read file into string $file = file_get_contents($filename); if ($file && isOwnerOf($username,$filename)){
echo $file; return true;
} else{
echo 'You are not authorized to view this file';
} return false;
}
This code first reads a specified file into memory, then prints the file if the user is authorized to see its contents. The read of the file into memory may be resource intensive and is unnecessary if the user is not allowed to see the file anyway.
Example 3
The DTD and the very brief XML below illustrate what is meant by an XML bomb. The ZERO entity contains one character, the letter A. The choice of entity name ZERO is being used to indicate length equivalent to that exponent on two, that is, the length of ZERO is 2^0. Similarly, ONE refers to ZERO twice, therefore the XML parser will expand ONE to a length of 2, or 2^1. Ultimately, we reach entity THIRTYTWO, which will expand to 2^32 characters in length, or 4 GB, probably consuming far more data than expected.
(attack code)
Example Language: XML
<?xml version="1.0"?> <!DOCTYPE MaliciousDTD [ <!ENTITY ZERO "A"> <!ENTITY ONE "&ZERO;&ZERO;"> <!ENTITY TWO "&ONE;&ONE;"> ... <!ENTITY THIRTYTWO "&THIRTYONE;&THIRTYONE;"> ]> <data>&THIRTYTWO;</data>
Example 4
This example attempts to check if an input string is a "sentence" [REF-1164].
(bad code)
Example Language: JavaScript
var test_string = "Bad characters: $@#";
var bad_pattern = /^(\w+\s?)*$/i;
var result = test_string.search(bad_pattern);
The regular expression has a vulnerable backtracking clause inside (\w+\s?)*$ which can be triggered to cause a Denial of Service by processing particular phrases.
To fix the backtracking problem, backtracking is removed with the ?= portion of the expression which changes it to a lookahead and the \2 which prevents the backtracking. The modified example is:
(good code)
Example Language: JavaScript
var test_string = "Bad characters: $@#";
var good_pattern = /^((?=(\w+))\2\s?)*$/i;
var result = test_string.search(good_pattern);
Note that [REF-1164] has a more thorough (and lengthy) explanation of everything going on within the RegEx.
Example 5
An adversary can cause significant resource
consumption on a server by filtering the cryptographic
algorithms offered by the client to the ones that are the
most resource-intensive on the server side. After
discovering which cryptographic algorithms are supported
by the server, a malicious client can send the initial
cryptographic handshake messages that contains only the
resource-intensive algorithms. For some cryptographic
protocols, these messages can be completely
prefabricated, as the resource-intensive part of the
handshake happens on the server-side first (such as TLS),
rather than on the client side. In the case of
cryptographic protocols where the resource-intensive part
should happen on the client-side first (such as SSH), a
malicious client can send a forged/precalculated
computation result, which seems correct to the server, so
the resource-intensive part of the handshake is going to
happen on the server side. A malicious client is required
to send only the initial messages of a cryptographic
handshake to initiate the resource-consuming part of the
cryptographic handshake. These messages are usually
small, and generating them requires minimal computational
effort, enabling a denial-of-service attack. An
additional risk is the fact that higher key size
increases the effectiveness of the attack. Cryptographic
protocols where the clients have influence over the size
of the used key (such as TLS 1.3 or SSH) are most at
risk, as the client can enforce the highest key size
supported by the server.
Diffie-Hellman (DHE) Key Agreement Protocol allows attackers to send arbitrary numbers that are not public keys, which causes the server to perform expensive, unnecessary computation of modular exponentiation.
The Diffie-Hellman Key Agreement Protocol allows use of long exponents, which are more computationally expensive than using certain "short exponents" with particular properties.
Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
Submitted content that led to modifications in applicable platforms, common consequences, potential mitigations, demonstrative examples, observed examples.
Description
This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
