CVE-2008-4762 in FreeSSHD
Summary
by MITRE
Stack-based buffer overflow in freeSSHd 1.2.1 allows remote authenticated users to cause a denial of service (service crash) and potentially execute arbitrary code via a long argument to the (1) rename and (2) realpath parameters.
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Analysis
by VulDB Data Team • 05/25/2025
The vulnerability identified as CVE-2008-4762 represents a critical stack-based buffer overflow flaw within freeSSHd version 1.2.1 that affects the Secure Shell implementation. This issue specifically targets two command parameters: rename and realpath, which are part of the SSH server's file manipulation functionality. The vulnerability stems from inadequate input validation mechanisms that fail to properly check the length of user-supplied arguments before processing them within fixed-size stack buffers. This particular implementation flaw creates an exploitable condition where malicious input can overwrite adjacent memory locations, leading to unpredictable system behavior. The vulnerability is particularly concerning because it requires only authenticated access, meaning that an attacker who has already established a valid SSH session can leverage this flaw to compromise the system. From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite stack data. The attack vector operates through the SSH protocol itself, making it a significant concern for network security infrastructure that relies on SSH services for remote access and management.
The technical exploitation of this vulnerability involves sending specially crafted arguments that exceed the allocated buffer space for the rename and realpath parameters. When the SSH server processes these long arguments, the stack-based buffer overflow occurs as the program attempts to write data beyond the predefined memory boundaries. This overflow can corrupt the return addresses of function calls, leading to service crashes or potentially allowing attackers to inject and execute arbitrary code within the context of the SSH service. The impact extends beyond simple denial of service since successful exploitation could result in complete system compromise, particularly if the SSH service runs with elevated privileges. This vulnerability demonstrates poor defensive programming practices and highlights the importance of implementing proper input sanitization and bounds checking mechanisms. The ATT&CK framework categorizes this type of vulnerability under T1203, which involves the exploitation of software vulnerabilities to gain access to systems, and T1059, which covers command and scripting interpreters used to establish persistence or execute commands. The vulnerability's remote nature means that exploitation can occur from anywhere on the network, provided the attacker has valid authentication credentials, making it particularly dangerous in enterprise environments.
The operational impact of CVE-2008-4762 extends beyond immediate service disruption to encompass potential data integrity compromise and unauthorized system access. Organizations running affected versions of freeSSHd face significant risk of unauthorized access, data exfiltration, and system compromise if this vulnerability is exploited. The vulnerability affects the core functionality of the SSH service, potentially rendering the system inaccessible to legitimate users while providing attackers with a foothold for further reconnaissance and lateral movement. Security teams must consider this vulnerability in their risk assessments and incident response planning, as it represents a known exploit that can be leveraged by threat actors without requiring advanced technical skills. The exploitation of this vulnerability can occur through automated scanning tools that identify vulnerable SSH implementations, making it a target for widespread exploitation across networks. Mitigation strategies should include immediate patching of the freeSSHd software to version 1.2.2 or later, which contains the necessary fixes for the buffer overflow conditions. Additionally, organizations should implement network segmentation, access controls, and monitoring solutions to detect and prevent exploitation attempts. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that include regular vulnerability assessments and security audits to identify and remediate similar issues before they can be exploited by malicious actors.