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.)
CWE-296 Base Draft
Improper Following of a Certificate's Chain of Trust
This vulnerability occurs when software fails to properly validate the entire certificate chain back to a trusted root authority. This mistake can cause the system to incorrectly trust a certificate…
Definition
What is CWE-296?
This vulnerability occurs when software fails to properly validate the entire certificate chain back to a trusted root authority. This mistake can cause the system to incorrectly trust a certificate and the resource it represents, creating a security gap.
A certificate's trustworthiness isn't inherent; it's derived from a verifiable chain linking it back to a root certificate you already trust. If your code only checks the first link—or skips any intermediate certificates—you haven't actually verified the chain. This is like trusting an ID card because it looks official, without checking if the issuing authority is legitimate and properly authorized the person who issued it.
The chain can break in several common ways. These include accepting a self-signed certificate (unless it's the designated root), failing to validate every intermediate certificate's constraints and signatures, or relying on a root certificate that has been compromised. Each skipped check creates an opportunity for an attacker to present a fraudulent certificate that your software will incorrectly accept as valid.
Real-world impact
Real-world CVEs caused by CWE-296
-
Server allows bypass of certificate pinning by sending a chain of trust that includes a trusted CA that is not pinned.
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Verification function trusts certificate chains in which the last certificate is self-signed.
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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).
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Web browser does not check if any intermediate certificates are revoked.
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chain: DNS server does not correctly check return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
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chain: incorrect check of return value from the OpenSSL EVP_VerifyFinal function allows bypass of validation of the certificate chain.
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File-transfer software does not validate Basic Constraints of an intermediate CA-signed certificate.
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Cryptographic API, as used in web browsers, mail clients, and other software, does not properly validate Basic Constraints.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable C
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* Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-296
- 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.
Detection signals
How to detect CWE-296
Plexicus auto-detects CWE-296 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-296?
How serious is CWE-296?
What languages or platforms are affected by CWE-296?
How can I prevent CWE-296?
How does Plexicus detect and fix CWE-296?
Where can I learn more about CWE-296?
Frequently asked questions
What is CWE-296?
This vulnerability occurs when software fails to properly validate the entire certificate chain back to a trusted root authority. This mistake can cause the system to incorrectly trust a certificate and the resource it represents, creating a security gap.
How serious is CWE-296?
MITRE rates the likelihood of exploit as Low — exploitation is uncommon, but the weakness should still be fixed when discovered.
What languages or platforms are affected by CWE-296?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-296?
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.
How does Plexicus detect and fix CWE-296?
Plexicus's SAST engine matches the data-flow signature for CWE-296 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-296?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/296.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-296
CWE-295 Parent
Improper Certificate Validation
This vulnerability occurs when an application fails to properly verify the authenticity of a digital certificate, or performs the…
CWE-297 Sibling
Improper Validation of Certificate with Host Mismatch
This vulnerability occurs when an application accepts a valid SSL/TLS certificate without properly verifying that it actually belongs to…
CWE-298 Sibling
Improper Validation of Certificate Expiration
This vulnerability occurs when an application fails to properly check if a digital certificate has expired, potentially trusting…
CWE-299 Sibling
Improper Check for Certificate Revocation
This vulnerability occurs when an application fails to properly verify whether a security certificate has been revoked, potentially…
CWE-599 Sibling
Missing Validation of OpenSSL Certificate
This vulnerability occurs when an application uses OpenSSL but fails to properly verify server certificates by not calling…
Resources
Further reading
- MITRE — official CWE-296 https://cwe.mitre.org/data/definitions/296.html
- The CLASP Application Security Process https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf
- The Most Dangerous Code in the World: Validating SSL Certificates in Non-Browser Software https://www.cs.utexas.edu/~shmat/shmat_ccs12.pdf
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