CVE-2006-3121 in heartbeat
Summary
by MITRE
The peel_netstring function in cl_netstring.c in the heartbeat subsystem in High-Availability Linux before 1.2.5, and 2.0 before 2.0.7, allows remote attackers to cause a denial of service (crash) via the length parameter in a heartbeat message.
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Analysis
by VulDB Data Team • 01/23/2025
The CVE-2006-3121 vulnerability represents a critical denial of service flaw within the heartbeat subsystem of High-Availability Linux platforms. This vulnerability specifically targets the peel_netstring function located in the cl_netstring.c file, which serves as a core component for handling network string operations within the high-availability infrastructure. The heartbeat subsystem is fundamental to maintaining cluster integrity and failover capabilities in high-availability environments, making this vulnerability particularly dangerous as it can compromise the entire cluster's operational stability.
The technical flaw manifests through improper validation of the length parameter within heartbeat messages. When a malformed heartbeat message containing an invalid or excessively large length parameter is processed by the peel_netstring function, the system fails to properly handle the boundary conditions, leading to a crash of the heartbeat daemon. This occurs because the function does not adequately validate input parameters before attempting to process network data, creating a classic buffer over-read or integer overflow condition. The vulnerability falls under the CWE-129 weakness category, which specifically addresses issues related to insufficient validation of length parameters in data processing functions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise high-availability cluster integrity. When the heartbeat daemon crashes due to maliciously crafted heartbeat messages, the cluster nodes lose their ability to communicate health status to each other, potentially triggering unnecessary failover events or leaving the cluster in an inconsistent state. This can result in extended downtime, data inconsistency issues, and potential service degradation for applications relying on the high-availability infrastructure. From an attacker's perspective, this represents a low-effort, high-impact method for disrupting critical infrastructure, as the attack requires only the ability to send specially crafted network messages to the heartbeat port.
The vulnerability aligns with several ATT&CK framework techniques including T1499.004 for Network Denial of Service and T1595.001 for Network Scanning, as exploitation requires network access and can be automated to target multiple systems. Organizations implementing High-Availability Linux solutions should prioritize immediate patching to versions 1.2.5 and 2.0.7 respectively, as these releases contain the necessary input validation fixes. Additionally, network segmentation and firewall rules should be implemented to restrict heartbeat traffic to trusted nodes only, reducing the attack surface. The fix typically involves adding proper input validation checks before processing length parameters, ensuring that all numeric values fall within acceptable ranges and implementing bounds checking to prevent buffer overflows. This vulnerability underscores the critical importance of input validation in distributed systems and highlights how seemingly minor flaws in core infrastructure components can lead to significant operational disruptions.