CVE-2015-0288 in OpenSSL
Summary
by MITRE
The X509_to_X509_REQ function in crypto/x509/x509_req.c in OpenSSL before 0.9.8zf, 1.0.0 before 1.0.0r, 1.0.1 before 1.0.1m, and 1.0.2 before 1.0.2a might allow attackers to cause a denial of service (NULL pointer dereference and application crash) via an invalid certificate key.
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Analysis
by VulDB Data Team • 04/15/2022
The vulnerability identified as CVE-2015-0288 represents a critical denial of service flaw within the OpenSSL cryptographic library that affects multiple version streams including 0.9.8, 1.0.0, 1.0.1, and 1.0.2 series. This issue manifests specifically within the X509_to_X509_REQ function located in the crypto/x509/x509_req.c file, where improper handling of invalid certificate keys leads to application instability. The flaw stems from a NULL pointer dereference condition that occurs when the function processes malformed certificate data, creating a scenario where legitimate applications using OpenSSL may crash unexpectedly.
The technical implementation of this vulnerability involves the X509_to_X509_REQ function failing to properly validate certificate key structures before attempting to process them. When an attacker provides an invalid certificate key structure, the function attempts to dereference a NULL pointer, resulting in an application crash. This behavior aligns with CWE-476, which categorizes NULL pointer dereference as a common weakness in software security. The vulnerability operates at the cryptographic layer where certificate processing occurs, making it particularly dangerous for systems that rely heavily on SSL/TLS certificate validation and management.
From an operational perspective, this vulnerability presents significant risks to systems that utilize OpenSSL for certificate processing and validation tasks. Any application that accepts or processes X509 certificates from untrusted sources could become vulnerable to this denial of service attack, potentially affecting web servers, email systems, and other cryptographic services. The impact extends beyond simple service disruption as attackers could exploit this weakness to repeatedly crash services, leading to prolonged availability issues and potential business disruption. This vulnerability particularly affects systems that process certificate requests or perform certificate validation as part of their normal operations.
The mitigation strategy for CVE-2015-0288 involves immediate deployment of patched OpenSSL versions that address the NULL pointer dereference issue. Organizations should prioritize updating to OpenSSL versions 0.9.8zf, 1.0.0r, 1.0.1m, or 1.0.2a, which contain the necessary code modifications to properly handle invalid certificate keys. Additionally, implementing proper input validation and sanitization measures at application layers can provide defense-in-depth protection. Security teams should also consider monitoring for unusual certificate processing patterns that might indicate exploitation attempts. This vulnerability demonstrates the importance of proper error handling in cryptographic libraries and aligns with ATT&CK technique T1499.004 for denial of service attacks, where adversaries leverage software weaknesses to disrupt service availability. The remediation process should include comprehensive testing to ensure that patched versions maintain expected functionality while eliminating the vulnerability.