CVE-2016-7144 in UnrealIRCd
Summary
by MITRE
The m_authenticate function in modules/m_sasl.c in UnrealIRCd before 3.2.10.7 and 4.x before 4.0.6 allows remote attackers to spoof certificate fingerprints and consequently log in as another user via a crafted AUTHENTICATE parameter.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-7144 represents a critical authentication bypass flaw in UnrealIRCd, a widely deployed Internet Relay Chat server software. This issue affects versions prior to 3.2.10.7 and 4.x prior to 4.0.6, making it a persistent threat across multiple major versions of the software. The vulnerability specifically resides within the m_authenticate function located in the modules/m_sasl.c file, which handles SASL (Simple Authentication and Security Layer) authentication mechanisms. The flaw enables remote attackers to manipulate the authentication process through carefully crafted AUTHENTICATE parameters, fundamentally compromising the integrity of user authentication.
The technical nature of this vulnerability stems from insufficient validation of certificate fingerprints during the authentication process. When users attempt to authenticate using SASL with certificate-based authentication, the system should rigorously verify that the presented certificate matches the expected fingerprint for the target user account. However, the m_authenticate function fails to properly validate these cryptographic signatures, allowing attackers to substitute their own certificate fingerprints for those of legitimate users. This creates a scenario where an attacker can present a forged certificate that appears to belong to another user, effectively impersonating that user within the IRC network. The vulnerability operates at the protocol level, exploiting weaknesses in how certificate validation is implemented rather than targeting network infrastructure or system-level components.
The operational impact of CVE-2016-7144 extends far beyond simple unauthorized access, as it enables sophisticated attacks that can compromise entire IRC networks. Attackers can leverage this vulnerability to gain administrative privileges, manipulate chat messages, access private channels, and potentially use the compromised accounts as entry points for further network infiltration. The ability to spoof certificate fingerprints means that even users with properly configured certificate-based authentication can be bypassed, undermining the security model that relies on cryptographic proof of identity. This vulnerability particularly affects networks that depend on certificate-based authentication for user verification, as it directly undermines the trust model that certificate-based systems are designed to provide. The impact is amplified in environments where IRC servers serve as communication platforms for sensitive operations or where multiple users with varying permission levels collaborate.
Organizations and system administrators should immediately implement mitigations including upgrading to UnrealIRCd versions 3.2.10.7 or 4.0.6, which contain the necessary patches to address the certificate validation flaw. The vulnerability aligns with CWE-287, which addresses improper handling of authentication tokens, and maps to ATT&CK technique T1078 for valid accounts usage, as attackers can effectively use stolen or forged authentication credentials to maintain persistent access. Additional defensive measures include implementing network segmentation to limit exposure, monitoring authentication logs for suspicious patterns, and establishing robust certificate management procedures. The patch addresses the core validation issue by ensuring that certificate fingerprints are properly verified against stored values before granting authentication access, thereby preventing the manipulation of certificate-based authentication mechanisms. Regular security audits of IRC server configurations should be conducted to ensure that all authentication mechanisms are properly configured and that no legacy or insecure configurations remain in place.