CWE-1204: Generation of Weak Initialization Vector (IV)
Weakness ID: 1204
Vulnerability Mapping:ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction:
BaseBase - 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.
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Description
The product uses a cryptographic primitive that uses an Initialization
Vector (IV), but the product does not generate IVs that are
sufficiently unpredictable or unique according to the expected
cryptographic requirements for that primitive.
Extended Description
By design, some cryptographic primitives
(such as block ciphers) require that IVs
must have certain properties for the
uniqueness and/or unpredictability of an
IV. Primitives may vary in how important
these properties are. If these properties
are not maintained, e.g. by a bug in the
code, then the cryptography may be weakened
or broken by attacking the IVs themselves.
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.
Scope
Impact
Likelihood
Confidentiality
Technical Impact: Read Application Data
If the IV is not properly initialized, data that is encrypted can be compromised and information about the data can be leaked. See [REF-1179].
Potential Mitigations
Phase: Implementation
Different cipher
modes have different requirements for
their IVs. When choosing and implementing
a mode, it is important to understand
those requirements in order to keep
security guarantees intact. Generally, it
is safest to generate a random IV, since
it will be both unpredictable and have a
very low chance of being non-unique. IVs
do not have to be kept secret, so if
generating duplicate IVs is a concern, a
list of already-used IVs can be kept and
checked against.
NIST offers recommendations on generation of IVs for modes of which they have approved. These include options for when random IVs are not practical. For CBC, CFB, and OFB, see [REF-1175]; for GCM, see [REF-1178].
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.
Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.
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 "Software Development" (CWE-699)
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
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
Implementation
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)
Demonstrative Examples
Example 1
In the following examples, CBC mode is used when encrypting data:
In both of these examples, the initialization vector (IV) is always a block of zeros. This makes the resulting cipher text much more predictable and susceptible to a dictionary attack.
Example 2
The Wired Equivalent Privacy (WEP) protocol used in the 802.11
wireless standard only supported 40-bit keys, and the IVs were only 24
bits, increasing the chances that the same IV would be reused for
multiple messages. The IV was included in plaintext as part of the packet, making
it directly observable to attackers. Only 5000 messages are needed
before a collision occurs due to the "birthday paradox" [REF-1176]. Some
implementations would reuse the same IV for each packet. This IV reuse
made it much easier for attackers to recover plaintext from
two packets with the same IV, using well-understood attacks,
especially if the plaintext was known for one of the packets [REF-1175].
BEAST attack in SSL 3.0 / TLS 1.0. In CBC mode, chained initialization vectors are non-random, allowing decryption of HTTPS traffic using a chosen plaintext attack.
encryption functionality in an authentication framework uses a fixed null IV with CBC mode, allowing attackers to decrypt traffic in applications that use this functionality
Blowfish-CBC implementation constructs an IV where each byte is calculated modulo 8 instead of modulo 256, resulting in less than 12 bits for the effective IV length, and less than 4096 possible IV values.
Functional Areas
Cryptography
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.
(this CWE ID may be used to map to real-world vulnerabilities)
Reason:
Acceptable-Use
Rationale:
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comments:
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
Notes
Maintenance
As of CWE 4.5, terminology related to randomness, entropy, and
predictability can vary widely. Within the developer and other
communities, "randomness" is used heavily. However, within
cryptography, "entropy" is distinct, typically implied as a
measurement. There are no commonly-used definitions, even within
standards documents and cryptography papers. Future versions of
CWE will attempt to define these terms and, if necessary,
distinguish between them in ways that are appropriate for
different communities but do not reduce the usability of CWE for
mapping, understanding, or other scenarios.
[REF-1175] Nikita Borisov, Ian Goldberg and David Wagner. "Intercepting Mobile Communications: The Insecurity of 802.11". 3. Risks of Keystream Reuse. Proceedings of the Seventh Annual International Conference on Mobile Computing And Networking. ACM. 2001-07.
<http://www.isaac.cs.berkeley.edu/isaac/mobicom.pdf>.
[REF-1175] Nikita Borisov, Ian Goldberg and David Wagner. "Intercepting Mobile Communications: The Insecurity of 802.11". Appendix C. Proceedings of the Seventh Annual International Conference on Mobile Computing And Networking. ACM. 2001-07.
<http://www.isaac.cs.berkeley.edu/isaac/mobicom.pdf>.
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.
