CVE-2003-0826 in lsh Daemon
Summary
by MITRE
lsh daemon (lshd) does not properly return from certain functions in (1) read_line.c, (2) channel_commands.c, or (3) client_keyexchange.c when long input is provided, which could allow remote attackers to execute arbitrary code via a heap-based buffer overflow attack.
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Analysis
by VulDB Data Team • 07/21/2025
The lsh daemon vulnerability identified as CVE-2003-0826 represents a critical heap-based buffer overflow condition affecting the lshd service implementation. This flaw manifests in three specific source files within the lsh daemon codebase: read_line.c, channel_commands.c, and client_keyexchange.c. The vulnerability arises from improper function return handling when processing lengthy input sequences, creating exploitable conditions that can be leveraged by remote attackers to execute arbitrary code on affected systems. The issue stems from inadequate input validation and boundary checking mechanisms that fail to properly manage memory allocation during function execution. When maliciously crafted long input is processed through these vulnerable functions, the daemon's memory management routines become corrupted, leading to potential code execution privileges for remote attackers.
The technical exploitation of this vulnerability involves crafting input sequences that exceed the allocated buffer sizes in the targeted source files, causing memory corruption through heap overflow conditions. The flaw specifically affects the lsh daemon's ability to handle extended input data during authentication and communication processes, particularly during key exchange operations and command processing. Attackers can leverage this vulnerability to overwrite critical memory locations, potentially redirecting execution flow to malicious code injected into the heap memory space. This type of vulnerability aligns with CWE-121, heap-based buffer overflow conditions, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under technique T1059 for command and script injection. The vulnerability's impact is particularly severe as it allows for remote code execution without requiring authentication, making it a prime target for automated exploitation tools.
The operational implications of CVE-2003-0826 extend beyond immediate code execution capabilities to encompass broader system compromise scenarios. Systems running vulnerable lsh daemon implementations become susceptible to complete takeover by remote adversaries who can leverage the heap overflow to gain elevated privileges and establish persistent access. The vulnerability affects the integrity and availability of the lsh service, potentially disrupting legitimate user communications and creating backdoor access points for further exploitation. Organizations utilizing lsh daemons for secure shell operations face significant risk exposure, as the vulnerability can be exploited by attackers without requiring prior access credentials or network proximity. The attack surface is particularly concerning given that lsh daemons typically operate on standard network ports and may be accessible from untrusted networks, amplifying the potential impact of successful exploitation attempts.
Mitigation strategies for this vulnerability require immediate implementation of software updates and patches provided by the vendor to address the buffer overflow conditions in the affected source files. System administrators should ensure that all lsh daemon installations are updated to versions containing proper input validation and boundary checking mechanisms. Network segmentation and firewall rules should be implemented to restrict access to lsh daemon services to trusted networks only, reducing exposure to remote exploitation attempts. Additionally, monitoring systems should be configured to detect unusual input patterns or connection attempts that may indicate exploitation attempts. The vulnerability's classification as heap-based buffer overflow aligns with industry best practices for memory safety, emphasizing the importance of input validation and proper resource management in security-critical applications. Organizations should implement comprehensive vulnerability management processes to identify and remediate similar issues in other network services and applications, ensuring overall system security posture remains robust against evolving exploitation techniques.