CWE-295 Base Borrador

Improper Certificate Validation

This vulnerability occurs when an application fails to properly verify the authenticity of a digital certificate, or performs the verification incorrectly, allowing untrusted connections to appear…

Definición

What is CWE-295?

This vulnerability occurs when an application fails to properly verify the authenticity of a digital certificate, or performs the verification incorrectly, allowing untrusted connections to appear legitimate.
Digital certificates act like digital passports for servers and services, proving their identity. When an application doesn't rigorously check these certificates—for example, by accepting self-signed certificates, ignoring expiration dates, or not validating the certificate chain back to a trusted root—it can mistakenly connect to a malicious server impersonating a legitimate one. This creates a critical opening for man-in-the-middle (MitM) attacks where attackers can intercept, read, or modify sensitive data in transit. To prevent this, developers must ensure their code enforces strict certificate validation. This means always verifying the certificate's signature chain against a trusted root certificate authority (CA), checking the hostname matches, and ensuring the certificate is valid and not revoked. Relying on default settings is often insufficient; explicit configuration in libraries for TLS/SSL connections is typically required to reject invalid certificates and maintain a secure communication channel.
Vulnerability Diagram CWE-295
Improper Certificate Validation Client verify=false MITM attacker presents fake cert CN: bank.com (not signed) decrypts + relays traffic bank.com real server Disabled or weak cert validation lets an attacker terminate TLS.
Impacto en el mundo real

Real-world CVEs caused by CWE-295

  • 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).

  • 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.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    This code checks the certificate of a connected peer.

  2. 2

    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.

  3. 3

    The following OpenSSL code obtains a certificate and verifies it.

  4. 4

    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.

  5. 5

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

Ejemplo de código vulnerable

Vulnerable C

This code checks the certificate of a connected peer.

Vulnerable C 
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*
Ejemplo de código seguro

Secure pseudo

Seguro 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.
Lista de prevención

How to prevent CWE-295

  • Architecture and Design / Implementation Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
  • 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 hostname.
Señales de detección

How to detect CWE-295

Automated Static Analysis - Binary or Bytecode SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis

Manual Static Analysis - Binary or Bytecode SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Dynamic Analysis with Automated Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Web Application Scanner

Dynamic Analysis with Manual Results Interpretation High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Man-in-the-middle attack tool

Manual Static Analysis - Source Code High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)

Automated Static Analysis - Source Code SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-295 y abre un PR de corrección en menos de 60 segundos.

Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-295?

This vulnerability occurs when an application fails to properly verify the authenticity of a digital certificate, or performs the verification incorrectly, allowing untrusted connections to appear legitimate.

¿Qué gravedad tiene CWE-295?

MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.

¿Qué lenguajes o plataformas se ven afectados por CWE-295?

MITRE lists the following affected platforms: Mobile.

¿Cómo puedo prevenir CWE-295?

Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key. If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.

¿Cómo detecta y corrige Plexicus CWE-295?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-295 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.

¿Dónde puedo aprender más sobre CWE-295?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/295.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-295

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Recursos

Further reading

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