Base weakness

Draft

CWE-295: Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

629

Recorded CVEs

With this primary weakness

KEVs

In the CISA KEV catalog

Not rated

Likelihood of exploit

Per MITRE

Base

Abstraction

MITRE classification

Overview

CWE-295 (Improper Certificate Validation) is a base-level software weakness catalogued by MITRE in the Common Weakness Enumeration (CWE). It describes a recurring type of mistake that can lead to exploitable security vulnerabilities.

Background

A certificate is a token that associates an identity (principal) to a cryptographic key. Certificates can be used to check if a public key belongs to the assumed owner.

Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

This code checks the certificate of a connected peer.

Vulnerable example

if ((cert = SSL_get_peer_certificate(ssl)) && host)

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.

The following OpenSSL code obtains a certificate and verifies it.

Vulnerable example

cert = SSL_get_peer_certificate(ssl);

Even though the "verify" step returns X509_V_OK, this step does not include checking the Common Name against the name of the host. That is, there is no guarantee that the certificate is for the desired host. The SSL connection could have been established with a malicious host that provided a valid certificate.

The following OpenSSL code ensures that there is a certificate and allows the use of expired certificates.

Vulnerable example

if (cert = SSL_get_peer(certificate(ssl)) {

If the call to SSL_get_verify_result() returns X509_V_ERR_CERT_HAS_EXPIRED, this means that the certificate has expired. As time goes on, there is an increasing chance for attackers to compromise the certificate.

The following OpenSSL code ensures that there is a certificate before continuing execution.

Vulnerable example

if (cert = SSL_get_peer_certificate(ssl)) {

Because this code does not use SSL_get_verify_results() to check the certificate, it could accept certificates that have been revoked (X509_V_ERR_CERT_REVOKED). The software could be communicating with a malicious host.

The following OpenSSL code ensures that the host has a certificate.

Vulnerable example

if (cert = SSL_get_peer_certificate(ssl)) {

Note that the code does not call SSL_get_verify_result(ssl), which effectively disables the validation step that checks the certificate.

Illustrative examples

Real CVEs that MITRE cites as examples of this weakness.

CVE-2019-12496 — A Go framework for robotics, drones, and IoT devices skips verification of root CA certificates by default.
CVE-2014-1266 — Chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint). The code's whitespace indentation did not reflect the actual control flow (CWE-1114) and did not explicitly delimit the block (CWE-483), which could have made it more difficult for human code auditors to detect the vulnerability.
CVE-2021-22909 — Chain: router's firmware update procedure uses curl with "-k" (insecure) option that disables certificate validation (CWE-295), allowing adversary-in-the-middle (AITM) compromise with a malicious firmware image (CWE-494).
CVE-2008-4989 — Verification function trusts certificate chains in which the last certificate is self-signed.
CVE-2012-5821 — 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)
CVE-2009-3046 — Web browser does not check if any intermediate certificates are revoked.
CVE-2011-0199 — Operating system does not check Certificate Revocation List (CRL) in some cases, allowing spoofing using a revoked certificate.
CVE-2012-5810 — Mobile banking application does not verify hostname, leading to financial loss.
CVE-2012-3446 — Cloud-support library written in Python uses incorrect regular expression when matching hostname.
CVE-2009-2408 — Web browser does not correctly handle '\0' character (NUL) in Common Name, allowing spoofing of https sites.
CVE-2012-2993 — Smartphone device does not verify hostname, allowing spoofing of mail services.
CVE-2012-5822 — Application uses third-party library that does not validate hostname.
CVE-2012-5819 — Cloud storage management application does not validate hostname.
CVE-2012-5817 — Java library uses JSSE SSLSocket and SSLEngine classes, which do not verify the hostname.
CVE-2010-1378 — Chain: incorrect calculation (CWE-682) allows attackers to bypass certificate checks (CWE-295)
CVE-2007-6746 — library for SSL and TLS does not check the activation or expiration dates of CA certificates
CVE-2005-3170 — LDAP client accepts certificates even if they are not from a trusted CA.
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.
CVE-2003-1229 — chain: product checks if client is trusted when it intended to check if the server is trusted, allowing validation of signed code.
CVE-2002-0862 — Cryptographic API, as used in web browsers, mail clients, and other software, does not properly validate Basic Constraints.
CVE-2009-1358 — chain: OS package manager does not check properly check the return value, allowing bypass using a revoked certificate.

CWE-295: Improper Certificate Validation

Overview

Background

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis - Binary or Bytecode

Manual Static Analysis - Binary or Bytecode

Dynamic Analysis with Automated Results Interpretation

Dynamic Analysis with Manual Results Interpretation

Manual Static Analysis - Source Code

Automated Static Analysis - Source Code

Architecture or Design Review

Code examples

Illustrative examples

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-295?

What CVEs are caused by CWE-295?

Is CWE-295 part of the OWASP Top 10?

How do you prevent CWE-295?

How is CWE-295 detected?

What are the consequences of CWE-295?

Is CWE-295 actively exploited?

References

Stay ahead of CWE-295

Overview

Background

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis - Binary or Bytecode

Manual Static Analysis - Binary or Bytecode

Dynamic Analysis with Automated Results Interpretation

Dynamic Analysis with Manual Results Interpretation

Manual Static Analysis - Source Code

Automated Static Analysis - Source Code

Architecture or Design Review

Code examples

Illustrative examples

Related weaknesses

Parent

Child

Peer

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-295?

What CVEs are caused by CWE-295?

Is CWE-295 part of the OWASP Top 10?

How do you prevent CWE-295?

How is CWE-295 detected?

What are the consequences of CWE-295?

Is CWE-295 actively exploited?

References

Stay ahead of CWE-295