CVE-1999-0478 in Sendmail
Summary
by MITRE
Denial of service in HP-UX sendmail 8.8.6 related to accepting connections.
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Analysis
by VulDB Data Team • 06/10/2024
The vulnerability identified as CVE-1999-0478 represents a critical denial of service flaw within HP-UX sendmail version 8.8.6, specifically targeting the mail transfer agent's connection handling mechanisms. This issue stems from inadequate input validation and connection management processes that occur during the initial connection acceptance phase of the sendmail service. The flaw manifests when the system receives malformed or specially crafted connection requests that cause the sendmail daemon to enter an unstable state, ultimately leading to service unavailability for legitimate users. The vulnerability exploits weaknesses in the protocol handling stack where the application fails to properly sanitize incoming connection parameters, creating a condition that can be triggered by remote attackers without requiring authentication or privileged access. This type of vulnerability falls under the broader category of improper input validation as classified by CWE-20, which specifically addresses weaknesses in how applications process input data. The impact extends beyond simple service disruption as it affects the fundamental reliability and availability of email services within HP-UX environments, potentially compromising business continuity and communication infrastructure.
The technical exploitation of this vulnerability occurs through the manipulation of connection establishment sequences that sendmail uses to accept incoming mail transactions. When the vulnerable sendmail daemon processes malformed connection requests, it fails to properly handle the connection state transitions, leading to resource exhaustion or memory corruption that results in process termination or indefinite hanging. The flaw specifically affects the TCP connection handling routines within the sendmail implementation, where insufficient error checking prevents the system from gracefully managing abnormal connection terminations or malformed protocol sequences. This vulnerability demonstrates characteristics consistent with CWE-121, which deals with stack-based buffer overflows, and CWE-122, which addresses heap-based buffer overflows, though the exact manifestation occurs at the protocol level rather than in traditional memory management contexts. The exploitation requires minimal privileges and can be executed remotely, making it particularly dangerous in production environments where email services are critical infrastructure components.
The operational impact of CVE-1999-0478 extends far beyond simple service disruption, as it represents a fundamental weakness in the email infrastructure that can be leveraged by malicious actors to create sustained denial of service conditions. Organizations relying on HP-UX systems with vulnerable sendmail installations face potential business disruption ranging from temporary email service outages to complete communication breakdowns that can affect customer relations, internal communications, and operational efficiency. The vulnerability's remote exploitability means that attackers can target systems without physical access or authentication credentials, making it particularly attractive for those seeking to disrupt services. From an attack framework perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1499 category, which covers network denial of service attacks, and specifically relates to T1498.1 for network denial of service via resource exhaustion. The attack surface is particularly wide given that sendmail is a widely deployed mail transfer agent, and the vulnerability affects multiple HP-UX versions, creating a significant risk across enterprise environments.
Mitigation strategies for CVE-1999-0478 require immediate system updates and configuration hardening measures to prevent exploitation. The primary recommended action involves upgrading to HP-UX sendmail versions that contain patches addressing the connection handling flaws, specifically versions that implement proper input validation and connection state management. Organizations should also implement network-level protections such as connection rate limiting, firewall rules that restrict access to mail services, and intrusion detection systems that can identify anomalous connection patterns. Configuration changes including disabling unnecessary mail service features, implementing connection timeouts, and establishing proper logging mechanisms can help detect and prevent exploitation attempts. Additionally, system administrators should consider implementing redundant mail services or load balancing solutions to maintain availability during potential exploitation events. The remediation process should include thorough testing of patched systems to ensure that the vulnerability is fully resolved without introducing compatibility issues with existing email infrastructure. Security monitoring should be enhanced to detect potential exploitation attempts through analysis of connection patterns, resource utilization spikes, and abnormal service behavior that may indicate successful exploitation of this denial of service vulnerability.