CVE-2009-2658 in ZNC
Summary
by MITRE
Directory traversal vulnerability in ZNC before 0.072 allows remote attackers to overwrite arbitrary files via a crafted DCC SEND request.
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Analysis
by VulDB Data Team • 02/03/2025
The vulnerability identified as CVE-2009-2658 represents a critical directory traversal flaw within the ZNC IRC bouncer software version 0.071 and earlier. This vulnerability specifically affects the DCC SEND functionality which is used for file transfers between IRC clients and servers. The flaw stems from inadequate input validation and sanitization within the DCC SEND request processing mechanism, allowing malicious actors to manipulate file paths and potentially overwrite arbitrary files on the server filesystem. This represents a significant security risk as it enables remote code execution and system compromise through simple network-based attacks.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious DCC SEND request containing directory traversal sequences such as ../ or ..\ in the filename parameter. The ZNC software fails to properly validate these sequences, allowing the attacker to navigate outside the intended directory boundaries and target files in other locations on the filesystem. This flaw directly maps to CWE-22, which defines improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The vulnerability demonstrates a classic lack of proper input validation and sanitization that violates fundamental security principles for handling user-supplied data.
From an operational impact perspective, this vulnerability creates severe consequences for organizations using vulnerable ZNC instances. Attackers can leverage this flaw to overwrite critical system files, modify configuration files, or even inject malicious code into the system. The remote nature of the attack means that adversaries do not require physical access or local system privileges to exploit the vulnerability. This makes it particularly dangerous as it can be exploited from anywhere on the internet, potentially leading to complete system compromise, data loss, or unauthorized access to sensitive information. The attack vector through DCC SEND also means that legitimate users may unknowingly facilitate these attacks through normal IRC operations.
Organizations should immediately upgrade to ZNC version 0.072 or later, which includes proper input validation and sanitization for DCC SEND requests. Additional mitigations include implementing network-level restrictions to limit access to DCC functionality, monitoring for unusual file transfer patterns, and configuring proper file permissions to limit the impact of potential exploitation. Security professionals should also consider implementing intrusion detection systems to monitor for directory traversal attempts and establish network segmentation to limit the attack surface. The vulnerability highlights the importance of proper input validation and the principle of least privilege in security design, aligning with ATT&CK technique T1059.007 for command and scripting interpreter and T1078.004 for valid accounts, as exploitation often requires legitimate user context to succeed.