The product generates and uses a predictable initialization Vector (IV) with Cipher Block Chaining (CBC) Mode, which causes algorithms to be susceptible to dictionary attacks when they are encrypted under the same key.

CBC mode eliminates a weakness of Electronic Code
Book (ECB) mode by allowing identical plaintext blocks to
be encrypted to different ciphertext blocks. This is
possible by the XOR-ing of an IV with the initial plaintext
block so that every plaintext block in the chain is XOR'd
with a different value before encryption. If IVs are
reused, then identical plaintexts would be encrypted to
identical ciphertexts. However, even if IVs are not
identical but are predictable, then they still break the
security of CBC mode against Chosen Plaintext Attacks
(CPA).

Primary

Resultant

CBC mode is a commonly used mode of operation for a
block cipher. It works by XOR-ing an IV with the initial
block of a plaintext prior to encryption and then
XOR-ing each successive block of plaintext with the
previous block of ciphertext before encryption.

C_0 = IV
C_i = E_k{M_i XOR C_{i-1}}

When used properly, CBC mode provides security against
chosen plaintext attacks. Having an unpredictable IV
is a crucial underpinning of this. See [REF-1171].

Implementation
Developers might dismiss the importance of an unpredictable IV and choose an easier implementation to save effort, weakening the scheme in the process.

Medium

Confidentiality
Read Application Data
If the IV is not properly initialized, data that is encrypted can be compromised and leak information.

Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
High

Implementation
NIST recommends two methods of generating unpredictable IVs for CBC mode [REF-1172]. The first is to generate the IV randomly. The second method is to encrypt a nonce with the same key and cipher to be used to encrypt the plaintext. In this case the nonce must be unique but can be predictable, since the block cipher will act as a pseudo random permutation.

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

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);

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/CBC/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.

CVE-2020-5408
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
https://www.cve.org/CVERecord?id=CVE-2020-5408

CVE-2017-17704
messages for a door-unlocking product use a fixed IV in CBC mode, which is the same after each restart
https://www.cve.org/CVERecord?id=CVE-2017-17704

CVE-2017-11133
application uses AES in CBC mode, but the pseudo-random secret and IV are generated using math.random, which is not cryptographically strong.
https://www.cve.org/CVERecord?id=CVE-2017-11133

CVE-2007-3528
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.
https://www.cve.org/CVERecord?id=CVE-2007-3528

CVE-2011-3389
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.
https://www.cve.org/CVERecord?id=CVE-2011-3389

Cryptography

Not using a random IV with CBC mode

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
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.

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.

CLASP
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Background_Details, Common_Consequences, Functional_Areas, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated References, Relationships

CWE Content Team
MITRE
2012-10-30
updated Demonstrative_Examples, Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Applicable_Platforms, Demonstrative_Examples

CWE Content Team
MITRE
2019-06-20
updated Demonstrative_Examples

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2021-03-15
updated Background_Details, Common_Consequences, Demonstrative_Examples, Description, Modes_of_Introduction, Name, Observed_Examples, Potential_Mitigations, References, Relationships

CWE Content Team
MITRE
2021-07-20
updated Description, Maintenance_Notes, Name, References

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2022-04-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Applicable_Platforms

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, Modes_of_Introduction, Relationships, Time_of_Introduction

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Relationships, Weakness_Ordinalities

Not Using a Random IV with CBC Mode
Not Using an Unpredictable IV with CBC Mode