CVE-2004-0826 in Network Security Services Library
Summary
by MITRE
Heap-based buffer overflow in Netscape Network Security Services (NSS) library allows remote attackers to execute arbitrary code via a modified record length field in an SSLv2 client hello message.
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Analysis
by VulDB Data Team • 06/29/2019
The vulnerability described in CVE-2004-0826 represents a critical heap-based buffer overflow within the Netscape Network Security Services (NSS) library, a fundamental cryptographic component used by numerous applications including web browsers, email clients, and security tools. This flaw exists in the SSLv2 protocol implementation where the NSS library fails to properly validate the record length field in SSLv2 client hello messages, creating a condition where maliciously crafted data can overwrite adjacent memory locations in the heap. The vulnerability specifically affects the processing of SSLv2 client hello records, which are the initial messages exchanged during SSL version 2.0 handshakes between clients and servers. The heap-based nature of this overflow means that memory corruption occurs in the heap memory space rather than on the stack, making exploitation more complex but potentially more reliable for achieving arbitrary code execution.
The technical exploitation of this vulnerability requires an attacker to send a specially crafted SSLv2 client hello message containing a modified record length field that exceeds the expected buffer boundaries. When the NSS library processes this malformed data, it allocates memory based on the inflated length field without proper bounds checking, resulting in a buffer overflow that can overwrite critical heap metadata or adjacent memory structures. This memory corruption can be leveraged to overwrite function pointers, return addresses, or other control data structures, ultimately allowing an attacker to redirect program execution flow and inject malicious code. The vulnerability is particularly dangerous because SSLv2 protocol support was widely implemented across various applications, making numerous systems susceptible to exploitation through a single malformed network packet. The attack vector is entirely remote, requiring no local access or authentication, and can be executed against any system running an application that utilizes the vulnerable NSS library.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a serious threat to the integrity and confidentiality of network communications. Systems that rely on NSS for SSL/TLS functionality, including web servers, email servers, and security appliances, could be compromised through this vulnerability. The exploitation of this flaw could result in complete system compromise, data theft, man-in-the-middle attacks, or the establishment of persistent backdoors. Organizations using applications such as Netscape Navigator, Mozilla Firefox, or any software that depends on NSS for cryptographic operations would be at risk. The vulnerability is particularly concerning because SSLv2 protocol support was often enabled by default in many applications, and the protocol itself was already considered insecure due to known cryptographic weaknesses. This combination of protocol insecurity and implementation flaws created a dangerous attack surface that could be exploited across a wide range of networked systems.
Mitigation strategies for CVE-2004-0826 require immediate action to disable SSLv2 protocol support and update affected systems to versions that contain patches for the heap overflow vulnerability. Organizations should implement network-level filtering to block SSLv2 traffic entirely, as this protocol is fundamentally insecure and should not be used in production environments. The recommended approach involves disabling SSLv2 support in all applications and services that utilize NSS, including web servers, email servers, and security appliances. Security patches from vendors should be applied immediately, with particular attention to the NSS library updates that address the buffer overflow condition. Additionally, network administrators should implement monitoring to detect unusual SSLv2 traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in cryptographic libraries, and aligns with CWE-121 heap-based buffer overflow weaknesses. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution through protocol manipulation and memory corruption attacks, emphasizing the need for robust application security practices and regular vulnerability assessments. The incident highlights the critical importance of maintaining up-to-date cryptographic libraries and the dangers of supporting deprecated protocols that contain known security flaws.