The product performs a key exchange with an actor without verifying the identity of that actor.
Performing a key exchange will preserve the integrity of the information sent between two entities, but this will not guarantee that the entities are who they claim they are. This may enable an attacker to impersonate an actor by modifying traffic between the two entities. Typically, this involves a victim client that contacts a malicious server that is impersonating a trusted server. If the client skips authentication or ignores an authentication failure, the malicious server may request authentication information from the user. The malicious server can then use this authentication information to log in to the trusted server using the victim's credentials, sniff traffic between the victim and trusted server, etc.

Primary

Architecture and Design
OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.

High

Access Control
Bypass Protection Mechanism
No authentication takes place in this process, bypassing an assumed protection of encryption.

Confidentiality
Read Application Data
The encrypted communication between a user and a trusted host may be subject to sniffing by any actor in the communication path.

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.)

Architecture and Design
Ensure that proper authentication is included in the system design.

Implementation
Understand and properly implement all checks necessary to ensure the identity of entities involved in encrypted communications.

Many systems have used Diffie-Hellman key exchange without authenticating the entities exchanging keys, allowing attackers to influence communications by redirecting or interfering with the communication path. Many people using SSL/TLS skip the authentication (often unknowingly).

Key exchange without entity authentication

Allowed
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.
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.

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 Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings

CWE Content Team
MITRE
2008-10-10
clarified the description

CWE Content Team
MITRE
2008-10-14
updated Description, Other_Notes

CWE Content Team
MITRE
2009-07-27
updated Relationships

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2011-06-27
updated Common_Consequences

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

CWE Content Team
MITRE
2013-02-21
updated Relationships

CWE Content Team
MITRE
2013-07-17
updated Applicable_Platforms, Relationships

CWE Content Team
MITRE
2014-07-30
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Modes_of_Introduction, Relationships

CWE Content Team
MITRE
2020-02-24
updated Common_Consequences, Demonstrative_Examples, Description, References, Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description, Relationships

CWE Content Team
MITRE
2023-04-27
updated Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

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