CVE-2003-0695 in OpenSSH
Summary
by MITRE
Multiple "buffer management errors" in OpenSSH before 3.7.1 may allow attackers to cause a denial of service or execute arbitrary code using (1) buffer_init in buffer.c, (2) buffer_free in buffer.c, or (3) a separate function in channels.c, a different vulnerability than CVE-2003-0693.
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Analysis
by VulDB Data Team • 08/11/2025
The vulnerability described in CVE-2003-0695 represents a critical buffer management flaw within OpenSSH versions prior to 3.7.1, exposing the SSH implementation to potential denial of service and arbitrary code execution attacks. This vulnerability stems from multiple buffer handling errors that occur during the initialization and cleanup phases of SSH communication processes, specifically affecting core components responsible for managing data buffers within the SSH protocol stack.
The technical exploitation of this vulnerability occurs through three distinct attack vectors that target fundamental buffer management functions within OpenSSH's codebase. The first vector involves buffer_init in buffer.c, where improper buffer allocation or initialization can lead to memory corruption issues that attackers can leverage to execute arbitrary code or cause system crashes. The second vector targets buffer_free in buffer.c, where inadequate buffer deallocation routines may result in memory management errors that can be exploited to trigger denial of service conditions or potentially execute malicious code. The third vector operates through a separate function in channels.c, which handles channel management during SSH sessions and represents a distinct vulnerability from CVE-2003-0693, indicating multiple independent buffer management flaws within the SSH implementation.
These buffer management errors fall under the broader category of memory corruption vulnerabilities, specifically aligning with CWE-122 which describes "Heap-based Buffer Overflow" and CWE-787 which addresses "Out-of-bounds Write." The operational impact of these vulnerabilities extends beyond simple service disruption, as successful exploitation can lead to complete system compromise through arbitrary code execution, making this a particularly dangerous vulnerability in network security contexts. Attackers can exploit these flaws by crafting specially crafted SSH packets that trigger the buffer management errors, potentially leading to remote code execution on vulnerable systems or forcing the SSH daemon to crash and restart, thereby causing denial of service.
The implications of this vulnerability within the ATT&CK framework demonstrate clear connections to multiple tactics including privilege escalation and denial of service, as attackers can leverage these buffer overflows to gain unauthorized access to systems or disrupt legitimate SSH services. The vulnerability particularly affects systems running older versions of OpenSSH where proper input validation and buffer boundary checking mechanisms were insufficient to prevent malicious data from corrupting memory structures. Organizations using SSH services would have been at significant risk, as these vulnerabilities could be exploited without requiring authentication, making them particularly dangerous in environments where SSH servers are exposed to untrusted networks. The remediation strategy involves immediate upgrading to OpenSSH 3.7.1 or later versions where these buffer management errors have been addressed through proper memory allocation, deallocation, and input validation procedures.
The vulnerability highlights fundamental security issues in buffer management practices within cryptographic implementations, where insufficient bounds checking and memory management can create exploitable conditions. These flaws underscore the importance of proper input validation and memory safety practices in security-critical software components, particularly in network protocols where attackers can directly influence buffer contents through network communication. The presence of multiple independent buffer management errors within the same software component indicates a systemic issue in the code review and testing processes, suggesting that more comprehensive security testing methodologies should be employed for cryptographic implementations. This vulnerability serves as a historical example of how seemingly minor buffer management issues can have significant security implications, particularly in widely deployed security tools like SSH implementations that form the backbone of secure network communications.