CVE-2006-0677 in Heimdal
Summary
by MITRE
telnetd in Heimdal 0.6.x before 0.6.6 and 0.7.x before 0.7.2 allows remote unauthenticated attackers to cause a denial of service (server crash) via unknown vectors that trigger a null dereference.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability identified as CVE-2006-0677 affects the telnetd service component within Heimdal Kerberos implementations version 0.6.x prior to 0.6.6 and 0.7.x prior to 0.7.2. This represents a critical security flaw that enables remote attackers to execute a denial of service attack against systems running vulnerable versions of the Heimdal Kerberos suite. The vulnerability specifically manifests through unknown vectors that ultimately result in a null dereference condition within the telnetd process, causing the service to crash and become unavailable to legitimate users.
The technical nature of this vulnerability stems from improper input validation and memory management within the telnetd implementation. A null dereference occurs when a program attempts to access a memory location referenced by a null pointer, which typically results in an immediate crash or segmentation fault. In the context of network services, this type of flaw represents a classic remote code execution vector that can be exploited by attackers without requiring authentication credentials. The vulnerability's classification under CWE-476 indicates it involves a null pointer dereference, which is a well-documented weakness in software development practices that can lead to service disruption and system instability.
From an operational perspective, this vulnerability poses significant risk to organizations relying on Heimdal Kerberos for authentication services. The telnetd service, when running on network-facing systems, becomes a prime target for automated scanning and exploitation attempts. Attackers can leverage this flaw to repeatedly crash the telnet daemon, effectively creating a persistent denial of service condition that disrupts legitimate network access and authentication services. The impact extends beyond simple service disruption as it can affect the broader Kerberos infrastructure, potentially compromising authentication workflows and creating opportunities for more sophisticated attacks. This vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks targeting services and infrastructure.
The exploitation of this vulnerability demonstrates the importance of proper software maintenance and patch management within enterprise environments. Organizations using Heimdal Kerberos implementations must urgently apply the available patches that address this null dereference issue in both the 0.6.6 and 0.7.2 release versions. System administrators should implement network segmentation to limit exposure of telnetd services and consider disabling the service entirely if it is not required for business operations. Additionally, monitoring and intrusion detection systems should be configured to identify potential exploitation attempts targeting this specific vulnerability pattern. The remediation process involves upgrading to patched versions of Heimdal Kerberos while ensuring proper testing to maintain service availability during the upgrade cycle. This vulnerability serves as a reminder of the critical importance of maintaining current security patches and implementing robust software supply chain security practices to prevent exploitation of known weaknesses in widely deployed authentication systems.