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Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

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ID

CWE-329: Not Using a Random IV with CBC Mode

Weakness ID: 329
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
Not using a random initialization Vector (IV) with Cipher Block Chaining (CBC) Mode causes algorithms to be susceptible to dictionary attacks.
+ Relationships

The table(s) below 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)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.573Improper Following of Specification by Caller
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.330Use of Insufficiently Random Values
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.310Cryptographic Issues
+ Background Details
CBC is the most commonly used mode of operation for a block cipher. It solves electronic code book's dictionary problems by XORing the ciphertext with plaintext. If it used to encrypt multiple data streams, dictionary attacks are possible, provided that the streams have a common beginning sequence.
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
The listings below show 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: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below 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.

ScopeImpactLikelihood
Confidentiality
Other

Technical Impact: Read Application Data; Other

If the CBC is not properly initialized, data that is encrypted can be compromised and therefore be read.
Integrity

Technical Impact: Modify Application Data

If the CBC is not properly initialized, encrypted data could be tampered with in transfer.
Access Control
Other

Technical Impact: Bypass Protection Mechanism; Other

Cryptographic based authentication systems could be defeated.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

In the following examples, CBC mode is used when encrypting data:

(bad code)
Example Language:
EVP_CIPHER_CTX ctx;
char key[EVP_MAX_KEY_LENGTH];
char iv[EVP_MAX_IV_LENGTH];
RAND_bytes(key, b);
memset(iv,0,EVP_MAX_IV_LENGTH);
EVP_EncryptInit(&ctx,EVP_bf_cbc(), key,iv);
(bad code)
Example Language: Java 
public class SymmetricCipherTest {
public static void main() {

byte[] text ="Secret".getBytes();
byte[] iv ={
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
};
KeyGenerator kg = KeyGenerator.getInstance("DES");
kg.init(56);
SecretKey key = kg.generateKey();
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
IvParameterSpec ips = new IvParameterSpec(iv);
cipher.init(Cipher.ENCRYPT_MODE, key, ips);
return cipher.doFinal(inpBytes);
}
}

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.

+ Potential Mitigations

Phase: Implementation

It is important to properly initialize CBC operating block ciphers or their utility is lost.
+ 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.959SFP Secondary Cluster: Weak Cryptography
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPNot using a random IV with CBC mode
+ References
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 2, "Initialization Vectors", Page 42. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganization
CLASP
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Background_Details, Common_Consequences, Functional_Areas, Relationships, Taxonomy_Mappings
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated References, Relationships
2012-10-30CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples

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Page Last Updated: March 29, 2018