CVE-2003-1069 in Solaris
Summary
by MITRE
The Telnet daemon (in.telnetd) for Solaris 2.6 through 9 allows remote attackers to cause a denial of service (CPU consumption by infinite loop).
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Analysis
by VulDB Data Team • 06/28/2021
The vulnerability identified as CVE-2003-1069 affects the Telnet daemon implementation in Solaris operating systems versions 2.6 through 9, representing a critical denial of service flaw that can be exploited remotely. This issue stems from a fundamental flaw in the in.telnetd process handling of certain network requests, specifically when processing malformed or specially crafted telnet protocol sequences. The vulnerability manifests as an infinite loop within the daemon's processing logic, causing sustained high CPU utilization that effectively renders the system unavailable to legitimate users. This flaw represents a classic example of a resource exhaustion attack that can be executed without authentication, making it particularly dangerous in networked environments where telnet services are exposed to untrusted networks. The vulnerability is categorized under CWE-835, which deals with infinite loops or infinite recursion, and aligns with ATT&CK technique T1499.1, specifically focusing on network denial of service attacks.
The technical exploitation of this vulnerability occurs when a remote attacker sends specific malformed input sequences to the telnet daemon, triggering an infinite loop in the protocol handling code. The in.telnetd process enters a continuous processing cycle where it repeatedly handles the same input without proper termination conditions, consuming 100% of available CPU resources and preventing legitimate connections from being established or maintained. This infinite loop typically occurs in the negotiation phase of the telnet protocol where the daemon processes terminal options and capabilities. The flaw is particularly insidious because it can be triggered through simple network connections without requiring any authentication credentials, making it an attractive target for attackers seeking to disrupt network services. The vulnerability affects systems where telnet services are actively running and accessible over the network, which was common in enterprise environments during the early 2000s when Solaris 2.6 through 9 were widely deployed.
The operational impact of CVE-2003-1069 extends beyond simple service disruption, as it can lead to cascading failures in network infrastructure and business operations. When the telnet daemon becomes unresponsive due to the infinite loop, it can affect other system services that depend on proper network connectivity, potentially causing broader system instability. Organizations that rely on telnet for administrative access or legacy applications may experience complete service outages, requiring manual intervention to restart the affected daemon processes. The vulnerability also exposes the underlying security architecture of older Solaris systems, demonstrating how protocol implementation flaws can create significant attack vectors. In enterprise environments, this could result in extended downtime for critical network services, potential data loss during service restoration, and increased operational costs for system administrators who must respond to the attack. The vulnerability highlights the importance of proper input validation and resource management in network services, particularly those that handle untrusted input from external sources.
Mitigation strategies for CVE-2003-1069 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves applying the appropriate security patches from Sun Microsystems, which typically include code modifications to prevent the infinite loop condition in the telnet daemon. Organizations should also implement network-level controls such as firewall rules that restrict access to telnet ports (typically port 23) to only trusted networks and IP addresses. Additionally, administrators should consider disabling telnet services entirely and migrating to more secure alternatives such as SSH, which provides encrypted communication and better authentication mechanisms. Network monitoring should be enhanced to detect unusual CPU utilization patterns that may indicate exploitation attempts. The vulnerability underscores the importance of following security best practices such as implementing proper input validation, using robust error handling mechanisms, and conducting regular security assessments of network services. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious telnet protocol sequences that may indicate exploitation attempts. For legacy systems where immediate patching is not feasible, network segmentation and access control measures provide essential protection against unauthorized exploitation of this vulnerability.