CWE-296: Improper Following of a Certificate's Chain of Trust
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.
View on MITREExtended Description
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.
Technical Details
- Structure
- Simple
Applicable To
Security Consequences
Scope
Impact
Exploitation of this flaw can lead to the trust of data that may have originated with a spoofed source.
Scope
Impact
Data, requests, or actions taken by the attacking entity can be carried out as a spoofed benign entity.
Mitigation Strategies
Phase
Description
Ensure that proper certificate checking is included in the system design.
Phase
Description
Understand, and properly implement all checks necessary to ensure the integrity of certificate trust integrity.
Phase
Description
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.
Detection Methods
No detection method information available for this CWE.
Code Examples & CVEs
Demonstrative Examples
This code checks the certificate of a connected peer.
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.
Observed CVE Examples (8)
Server allows bypass of certificate pinning by sending a chain of trust that includes a trusted CA that is not pinned.
View DetailsVerification function trusts certificate chains in which the last certificate is self-signed.
View DetailsChain: 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).
View Detailschain: DNS server does not correctly check return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
View Detailschain: incorrect check of return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
View DetailsFile-transfer software does not validate Basic Constraints of an intermediate CA-signed certificate.
View DetailsCryptographic API, as used in web browsers, mail clients, and other software, does not properly validate Basic Constraints.
View DetailsCWE Relationships
Frequently Asked Questions
What is CWE-296: Improper Following of a Certificate's Chain of Trust?+
CWE-296: Improper Following of a Certificate's Chain of Trust is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.
What are the security consequences of Improper Following of a Certificate's Chain of Trust?+
If exploited, CWE-296 (Improper Following of a Certificate's Chain of Trust) it can compromise Non-Repudiation, Integrity, Confidentiality, Availability and Access Control, leading to outcomes such as Hide Activities, Gain Privileges or Assume Identity and Execute Unauthorized Code or Commands.
How do you prevent or mitigate Improper Following of a Certificate's Chain of Trust?+
Recommended mitigations for CWE-296 include: Ensure that proper certificate checking is included in the system design. Understand, and properly implement all checks necessary to ensure the integrity of certificate trust integrity. 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.
Which programming languages are affected by Improper Following of a Certificate's Chain of Trust?+
CWE-296 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
What are real-world examples of Improper Following of a Certificate's Chain of Trust?+
MITRE documents real CVEs mapped to CWE-296, including CVE-2016-2402, CVE-2008-4989, CVE-2012-5821, CVE-2009-3046 and CVE-2009-0265. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
What is the difference between a CWE and a CVE?+
A CWE (Common Weakness Enumeration) like CWE-296 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.