The product does not follow, or incorrectly follows, the chain of trust for a certificate back to a trusted root certificate, resulting in incorrect trust of any resource that is associated with that certificate.

If a system does not follow the chain of trust of a certificate to a root server, the certificate loses all usefulness as a metric of trust. Essentially, the trust gained from a certificate is derived from a chain of trust -- with a reputable trusted entity at the end of that list. The end user must trust that reputable source, and this reputable source must vouch for the resource in question through the medium of the certificate.
In some cases, this trust traverses several entities who vouch for one another. The entity trusted by the end user is at one end of this trust chain, while the certificate-wielding resource is at the other end of the chain. If the user receives a certificate at the end of one of these trust chains and then proceeds to check only that the first link in the chain, no real trust has been derived, since the entire chain must be traversed back to a trusted source to verify the certificate.
There are several ways in which the chain of trust might be broken, including but not limited to:

Any certificate in the chain is self-signed, unless it the root.
Not every intermediate certificate is checked, starting from the original certificate all the way up to the root certificate.
An intermediate, CA-signed certificate does not have the expected Basic Constraints or other important extensions.
The root certificate has been compromised or authorized to the wrong party.

Primary

Implementation
When the product uses certificate pinning, the developer might not properly validate all relevant components of the certificate before pinning the certificate. This can make it difficult or expensive to test after the pinning is complete.

Implementation
REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Low

Non-Repudiation
Hide Activities
Exploitation of this flaw can lead to the trust of data that may have originated with a spoofed source.

Integrity
Confidentiality
Availability
Access Control
Gain Privileges or Assume Identity
Execute Unauthorized Code or Commands
Data, requests, or actions taken by the attacking entity can be carried out as a spoofed benign entity.

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

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

Implementation
Understand, and properly implement all checks necessary to ensure the integrity of certificate trust integrity.

Implementation
If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the full chain of trust.

This code checks the certificate of a connected peer.

if ((cert = SSL_get_peer_certificate(ssl)) && host)foo=SSL_get_verify_result(ssl);
if ((X509_V_OK==foo) || X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN==foo))

// certificate looks good, host can be trusted

In this case, because the certificate is self-signed, there was no external authority that could prove the identity of the host. The program could be communicating with a different system that is spoofing the host, e.g. by poisoning the DNS cache or using an Adversary-in-the-Middle (AITM) attack to modify the traffic from server to client.

CVE-2016-2402
Server allows bypass of certificate pinning by sending a chain of trust that includes a trusted CA that is not pinned.
https://www.cve.org/CVERecord?id=CVE-2016-2402

CVE-2008-4989
Verification function trusts certificate chains in which the last certificate is self-signed.
https://www.cve.org/CVERecord?id=CVE-2008-4989

CVE-2012-5821
Chain: Web browser uses a TLS-related function incorrectly, preventing it from verifying that a server's certificate is signed by a trusted certification authority (CA).
https://www.cve.org/CVERecord?id=CVE-2012-5821

CVE-2009-3046
Web browser does not check if any intermediate certificates are revoked.
https://www.cve.org/CVERecord?id=CVE-2009-3046

CVE-2009-0265
chain: DNS server does not correctly check return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
https://www.cve.org/CVERecord?id=CVE-2009-0265

CVE-2009-0124
chain: incorrect check of return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
https://www.cve.org/CVERecord?id=CVE-2009-0124

CVE-2002-0970
File-transfer software does not validate Basic Constraints of an intermediate CA-signed certificate.
https://www.cve.org/CVERecord?id=CVE-2002-0970

CVE-2002-0862
Cryptographic API, as used in web browsers, mail clients, and other software, does not properly validate Basic Constraints.
https://www.cve.org/CVERecord?id=CVE-2002-0862

Failure to follow chain of trust in certificate validation

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
2009-03-10
updated Description, Name, Relationships

CWE Content Team
MITRE
2009-05-27
updated Demonstrative_Examples

CWE Content Team
MITRE
2009-07-27
updated Demonstrative_Examples

CWE Content Team
MITRE
2010-12-13
updated Other_Notes

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

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

CWE Content Team
MITRE
2013-02-21
updated Applicable_Platforms, Demonstrative_Examples, Description, Name, Observed_Examples, Other_Notes, References, Relationships

CWE Content Team
MITRE
2013-07-17
updated Relationships

CWE Content Team
MITRE
2014-07-30
updated Demonstrative_Examples, Relationships

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

CWE Content Team
MITRE
2018-03-27
updated Modes_of_Introduction, Observed_Examples, Potential_Mitigations, Time_of_Introduction

CWE Content Team
MITRE
2019-09-19
updated Demonstrative_Examples

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

CWE Content Team
MITRE
2021-07-20
updated Demonstrative_Examples

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 Description, Modes_of_Introduction

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

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated References

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

Failure to Follow Chain of Trust in Certificate Validation
Improper Following of Chain of Trust for Certificate Validation