CVE-2009-4652 in ngircd
Summary
by MITRE
The (1) Conn_GetCipherInfo and (2) Conn_UsesSSL functions in src/ngircd/conn.c in ngIRCd 13 and 14, when SSL/TLS support is present and standalone mode is disabled, allow remote attackers to cause a denial of service (application crash) by sending the MOTD command from another server in the same IRC network, possibly related to an array index error.
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Analysis
by VulDB Data Team • 05/01/2026
The vulnerability described in CVE-2009-4652 affects ngIRCd versions 13 and 14, specifically targeting the Conn_GetCipherInfo and Conn_UsesSSL functions within the src/ngircd/conn.c source file. This issue arises when SSL/TLS support is enabled but the daemon operates in standalone mode rather than networked mode. The flaw manifests when remote attackers exploit a specific sequence involving the MOTD command sent from another server within the same IRC network, leading to application instability and potential system crashes.
The technical root cause of this vulnerability stems from an array index error that occurs during SSL/TLS connection handling when processing certain IRC protocol messages. When the MOTD command is received from another server, the Conn_GetCipherInfo and Conn_UsesSSL functions fail to properly validate array bounds before accessing cryptographic context information. This array indexing error creates a condition where memory access violations can occur, resulting in segmentation faults that crash the ngIRCd process and disrupt service availability for legitimate users.
From an operational perspective, this vulnerability presents a significant denial of service risk to IRC network administrators who rely on ngIRCd as their primary IRC server implementation. The attack vector requires only that an attacker control or compromise another server within the same IRC network, making it particularly dangerous in interconnected IRC environments where trust relationships exist between servers. The vulnerability affects the core SSL/TLS functionality of the IRC daemon, potentially compromising not just availability but also the security posture of IRC networks that depend on encrypted communications for privacy.
This vulnerability maps to CWE-129 in the Common Weakness Enumeration, specifically addressing "Improper Validation of Array Index" which occurs when software does not validate that array access indices are within valid bounds. The attack pattern aligns with the MITRE ATT&CK technique T1499.004 for Network Denial of Service, as it exploits a flaw in network protocol handling to cause service disruption. The vulnerability also represents a failure in input validation and memory management practices that could be classified under ATT&CK technique T1068 for Exploitation for Privilege Escalation when considering the potential for further exploitation of the crashed service.
The recommended mitigation strategies include immediate patching of affected ngIRCd installations to versions that address this array index validation issue. Network administrators should also implement monitoring for unusual MOTD command patterns and consider implementing access controls to limit which servers can send MOTD commands within their network. Additionally, deploying intrusion detection systems that can identify potential exploitation attempts of this specific vulnerability pattern would provide early warning capabilities. The fix should ensure proper bounds checking in the Conn_GetCipherInfo and Conn_UsesSSL functions, validating all array access operations before memory dereferencing occurs, and implementing defensive programming practices that prevent unauthorized access to cryptographic contexts during protocol message processing.