CVE-2016-7052 in Communications Diameter Signaling Router
Summary
by MITRE
crypto/x509/x509_vfy.c in OpenSSL 1.0.2i allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by triggering a CRL operation.
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Analysis
by VulDB Data Team • 01/04/2023
The vulnerability identified as CVE-2016-7052 resides within the OpenSSL 1.0.2i implementation in the x509_vfy.c file, specifically concerning Certificate Revocation List (CRL) processing operations. This flaw represents a critical denial of service vulnerability that can be exploited by remote attackers to crash applications relying on OpenSSL for secure communications. The vulnerability manifests when the application processes a malformed or specially crafted CRL that triggers a NULL pointer dereference during certificate verification operations.
The technical root cause of this vulnerability stems from inadequate input validation within the certificate verification logic. When OpenSSL encounters a CRL operation that contains malformed data or improper structure, the verification process fails to properly handle the exceptional condition, leading to a NULL pointer dereference. This occurs during the certificate chain validation phase where the system attempts to verify certificate revocation status against the provided CRL. The flaw is particularly insidious because it can be triggered through normal network operations without requiring authentication or special privileges, making it highly exploitable in real-world scenarios.
From an operational impact perspective, this vulnerability poses significant risks to systems that rely heavily on SSL/TLS certificate verification for secure communications. Applications such as web servers, email servers, and any system using OpenSSL for certificate validation become vulnerable to sustained denial of service attacks. An attacker can craft malicious CRL data that when processed by the vulnerable OpenSSL version will cause the target application to crash and restart, potentially leading to service disruption. The vulnerability affects the broader ecosystem of applications that depend on OpenSSL, including but not limited to web browsers, mail clients, and network infrastructure devices that implement certificate verification mechanisms.
The vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of improper input validation leading to application instability. From an attack framework perspective, this flaw maps to the denial of service category within the MITRE ATT&CK framework, specifically under the technique of service interruption. The attack surface is particularly broad as any application using OpenSSL 1.0.2i for certificate validation is potentially affected, regardless of the specific protocol or application layer being used.
Mitigation strategies for CVE-2016-7052 primarily involve upgrading to OpenSSL version 1.0.2j or later, which contains the necessary patches to address the NULL pointer dereference issue. Organizations should prioritize immediate patching of all systems running vulnerable OpenSSL versions, particularly those handling SSL/TLS communications or certificate validation processes. Additionally, implementing network-level monitoring to detect unusual CRL processing patterns can provide early warning of potential exploitation attempts. System administrators should also consider implementing certificate pinning mechanisms where appropriate and ensure that certificate validation processes include proper error handling and input sanitization to prevent similar vulnerabilities from manifesting in other components of the security infrastructure.