CVE-2002-1568 in OpenSSL
Summary
by MITRE
OpenSSL 0.9.6e uses assertions when detecting buffer overflow attacks instead of less severe mechanisms, which allows remote attackers to cause a denial of service (crash) via certain messages that cause OpenSSL to abort from a failed assertion, as demonstrated using SSLv2 CLIENT_MASTER_KEY messages, which are not properly handled in s2_srvr.c.
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Analysis
by VulDB Data Team • 06/29/2021
The vulnerability described in CVE-2002-1568 represents a critical design flaw in OpenSSL version 0.9.6e that fundamentally undermines the security and stability of SSL/TLS implementations. This issue specifically affects the SSLv2 protocol handling within the OpenSSL library, where the software employs assertions rather than graceful error handling mechanisms when encountering potentially malicious input. The vulnerability stems from the improper handling of SSLv2 CLIENT_MASTER_KEY messages in the s2_srvr.c source file, which serves as the server-side implementation for SSL version 2 protocol processing. When remote attackers craft specially malformed SSLv2 CLIENT_MASTER_KEY messages, the OpenSSL library fails to properly validate these inputs and instead triggers a fatal assertion failure that results in immediate program termination.
The technical implementation of this vulnerability demonstrates a fundamental misunderstanding of how security-critical code should handle malformed input. In the s2_srvr.c file, the OpenSSL implementation uses assertion checks that are designed to catch programming errors during development rather than to handle runtime anomalies from malicious input. This approach violates standard security practices and creates a predictable crash condition that attackers can exploit. When an assertion fails, the program terminates abruptly rather than attempting to recover or gracefully reject the malformed data, creating a classic denial of service scenario. The vulnerability specifically targets the SSLv2 protocol which, while deprecated, was still widely supported in 2002 and used in many production systems. This makes the impact particularly severe as attackers could easily disrupt services running on systems with OpenSSL 0.9.6e installations, especially those handling SSLv2 connections.
The operational impact of CVE-2002-1568 extends beyond simple service disruption to create significant reliability concerns for systems that depend on OpenSSL for secure communications. Organizations running vulnerable versions of OpenSSL would experience unexpected service outages whenever attackers successfully exploited this vulnerability, potentially leading to cascading failures in dependent services. The vulnerability is particularly dangerous because it requires minimal effort from attackers to trigger, as demonstrated by the specific SSLv2 CLIENT_MASTER_KEY message format. This makes it an attractive target for automated attacks and can lead to widespread service disruption across networks. The vulnerability also highlights the importance of proper error handling in cryptographic libraries, where defensive programming practices must account for malicious input rather than assuming benign data. The use of assertions for input validation represents a fundamental design flaw that violates established security principles and creates attack surfaces that could be leveraged for more sophisticated attacks.
The mitigation strategies for CVE-2002-1568 center around immediate software updates to newer versions of OpenSSL that properly handle malformed SSLv2 messages without triggering assertions. System administrators should prioritize upgrading to OpenSSL versions that implement proper error handling mechanisms and do not rely on assertions for input validation. Additionally, organizations should consider disabling SSLv2 support entirely on systems that do not require legacy compatibility, as this protocol is inherently insecure and has been deprecated for years. Network-level protections such as firewalls and intrusion detection systems can provide additional layers of defense by blocking suspicious SSLv2 traffic patterns, though these measures are secondary to proper software patching. The vulnerability serves as a historical example of how improper error handling in security-critical code can create exploitable conditions, emphasizing the need for robust defensive programming practices that follow industry standards such as those outlined in the CWE database. Organizations should implement comprehensive vulnerability management programs that regularly audit their cryptographic libraries and ensure that all security patches are applied promptly to prevent similar issues from compromising system integrity and availability.