CVE-2015-5333 in Mac OS X
Summary
by MITRE
Memory leak in the OBJ_obj2txt function in LibreSSL before 2.3.1 allows remote attackers to cause a denial of service (memory consumption) via a large number of ASN.1 object identifiers in X.509 certificates.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2015-5333 represents a critical memory leak flaw within the LibreSSL cryptographic library that affects versions prior to 2.3.1. This issue resides in the OBJ_obj2txt function which is responsible for converting ASN.1 object identifiers into their textual representation during X.509 certificate processing. The memory leak occurs when the library encounters a large number of ASN.1 object identifiers within X.509 certificates, causing excessive memory consumption that can ultimately lead to system resource exhaustion. The vulnerability specifically manifests when processing certificates containing numerous object identifiers, creating a condition where allocated memory is not properly released back to the system. This flaw falls under the CWE-401 category of inadequate resource management, where the application fails to properly manage memory allocation and deallocation processes. The attack vector is remote, meaning that unauthenticated attackers can exploit this vulnerability by presenting specially crafted X.509 certificates to systems running vulnerable LibreSSL implementations. This vulnerability directly maps to the ATT&CK technique T1499.004 which involves resource exhaustion attacks targeting memory consumption. The operational impact of this vulnerability extends beyond simple denial of service, as it can affect any service or application that relies on LibreSSL for certificate validation, including web servers, email servers, and SSL/TLS enabled applications. When exploited, the memory leak causes progressive memory consumption that can eventually lead to system instability, application crashes, or complete system unresponsiveness. The vulnerability is particularly dangerous in high-traffic environments where certificate validation occurs frequently, as the memory consumption accumulates rapidly with each processed certificate. The flaw demonstrates a classic example of how seemingly benign certificate processing operations can become a vector for resource exhaustion attacks. Organizations using vulnerable versions of LibreSSL are at risk of experiencing service degradation or complete service interruption when subjected to this type of attack. The memory leak affects the core certificate handling functionality of the library, making it a critical issue for any security infrastructure that depends on proper certificate validation. This vulnerability highlights the importance of proper memory management in cryptographic libraries and the potential for denial of service attacks to exploit seemingly minor implementation flaws. The impact is particularly severe because the vulnerability can be triggered without requiring authentication or specific user interaction, making it a significant concern for publicly accessible services. The flaw represents a failure in the library's resource management practices, specifically in how it handles the conversion of ASN.1 object identifiers to text format. When the OBJ_obj2txt function processes certificates with numerous object identifiers, it fails to properly release memory that was allocated for the textual representation of these identifiers. This creates a cumulative effect where each processed certificate contributes to growing memory consumption. The vulnerability affects the broader ecosystem of applications that depend on LibreSSL for secure communications, potentially impacting web services, email systems, and other networked applications. The memory leak behavior aligns with the ATT&CK tactic TA0040 which focuses on resource exhaustion as a method of attack. Remediation efforts must include immediate upgrading to LibreSSL version 2.3.1 or later, which contains the necessary patches to address the memory leak in the OBJ_obj2txt function. Additionally, organizations should implement monitoring for unusual memory consumption patterns in systems processing X.509 certificates, as this can serve as an early indicator of exploitation attempts. Network administrators should also consider implementing certificate validation policies that limit the number of object identifiers allowed in certificates or implement rate limiting for certificate processing operations. The vulnerability serves as a reminder of the critical importance of proper memory management in cryptographic libraries and the potential for subtle implementation flaws to create significant security risks. Organizations should conduct thorough vulnerability assessments to identify all systems running vulnerable versions of LibreSSL and ensure prompt remediation to prevent exploitation. The issue also underscores the necessity of regular security updates and the importance of maintaining current versions of cryptographic libraries to protect against known vulnerabilities.