CVE-2004-0079 in OpenSSL
Summary
by MITRE
The do_change_cipher_spec function in OpenSSL 0.9.6c to 0.9.6k, and 0.9.7a to 0.9.7c, allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference.
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Analysis
by VulDB Data Team • 01/22/2025
The vulnerability described in CVE-2004-0079 represents a critical denial of service flaw within the OpenSSL cryptographic library that affected versions ranging from 0.9.6c through 0.9.6k and 0.9.7a through 0.9.7c. This issue manifests during the SSL/TLS handshake process when the do_change_cipher_spec function encounters malformed input that leads to a null pointer dereference condition. The flaw specifically targets the cryptographic handshake mechanism that occurs when establishing secure connections between clients and servers, making it particularly dangerous as it can be exploited by remote attackers without requiring authentication or prior access to the system. The vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a fundamental programming error that occurs when software attempts to access memory through a pointer that has not been properly initialized or has been set to null.
The operational impact of this vulnerability extends beyond simple service disruption as it can cause complete application crashes or system instability when exploited. During an SSL/TLS handshake, when a malicious client sends specially crafted handshake messages that trigger the vulnerable do_change_cipher_spec function, the software fails to properly validate pointer references before dereferencing them, resulting in a segmentation fault or crash. This type of vulnerability directly impacts the availability aspect of the security triad, potentially allowing attackers to perform denial of service attacks against web servers, email servers, or any other service that relies on OpenSSL for secure communications. The attack surface is broad since OpenSSL was widely deployed across the internet for securing web traffic, email communications, and various other network services.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service and represents a classic example of how cryptographic library flaws can be weaponized for system disruption. The exploitability of this vulnerability is relatively straightforward as it requires only the ability to establish an SSL/TLS connection to the target service and send malformed handshake data. Security practitioners should note that this vulnerability was particularly concerning because it affected multiple versions of OpenSSL and could be exploited against any system running vulnerable software, making it a prime target for automated exploitation campaigns. The lack of authentication requirements and the broad deployment of affected OpenSSL versions meant that the potential impact was significant across enterprise networks and internet-facing services.
Mitigation strategies for CVE-2004-0079 focus primarily on immediate software updates and patches to the affected OpenSSL versions. Organizations should prioritize upgrading to OpenSSL versions 0.9.6l, 0.9.7d, or later releases that contain the necessary fixes for this null pointer dereference issue. Additionally, network administrators can implement temporary measures such as disabling SSL/TLS services or implementing connection rate limiting to reduce the impact of potential exploitation attempts. The vulnerability demonstrates the importance of thorough input validation in cryptographic libraries and highlights the critical need for security testing of core infrastructure components. System monitoring should be enhanced to detect unusual connection patterns or service disruptions that might indicate exploitation attempts, while also ensuring that all systems are regularly updated to protect against similar vulnerabilities that may be discovered in the future.