CVE-2010-0303 in Hybserv2
Summary
by MITRE
mystring.c in hybserv in IRCD-Hybrid (aka Hybrid2 IRC Services) 1.9.2 through 1.9.4 allows remote attackers to cause a denial of service (daemon crash) via a ":help \t" private message to the MemoServ service.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability identified as CVE-2010-0303 affects IRCD-Hybrid versions 1.9.2 through 1.9.4, specifically within the hybserv component's mystring.c file. This issue represents a classic buffer handling flaw that manifests when processing malformed input through the MemoServ service. The vulnerability occurs when a remote attacker sends a specially crafted private message containing a colon followed by a tab character to the MemoServ service, which triggers an unexpected daemon crash. The flaw resides in how the software processes string inputs without proper validation or bounds checking, creating an exploitable condition that can be leveraged for denial of service attacks.
From a technical perspective, this vulnerability demonstrates characteristics consistent with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The issue stems from inadequate input sanitization where the daemon fails to properly handle whitespace characters, particularly tab characters, in the context of command parsing. The tab character in the ":help " payload likely causes the string parsing routine to misinterpret the input boundaries, leading to memory corruption that ultimately results in daemon termination. This type of vulnerability falls under the ATT&CK technique T1499.004, which covers network denial of service attacks through service exhaustion or daemon crashes.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by malicious actors to repeatedly crash the MemoServ daemon, effectively rendering the service unavailable to legitimate users. This creates a persistent denial of service condition that can be maintained through repeated attacks without requiring authentication or advanced privileges. The vulnerability affects the broader IRCD-Hybrid ecosystem since MemoServ is a core component for message management and service coordination within IRC networks. Network administrators face significant challenges in maintaining service availability when such vulnerabilities exist, as the attacks can be easily automated and executed from any remote location without requiring specialized tools or extensive knowledge of the target system.
Mitigation strategies for this vulnerability should include immediate patching of affected IRCD-Hybrid installations to version 1.9.5 or later, which contains the necessary fixes for proper input validation. Additionally, implementing network-level filtering rules to block malformed IRC traffic, particularly around tab character sequences in private messages, can provide temporary protection. System administrators should also consider implementing intrusion detection systems that can identify and alert on suspicious IRC protocol patterns. The vulnerability highlights the importance of input validation in network services and demonstrates why proper bounds checking and sanitization routines are critical for maintaining service availability and system stability. Organizations should also conduct regular security assessments of their IRC infrastructure to identify similar vulnerabilities that may exist in other components of their network services stack.