CVE-2006-3085 in Linux
Summary
by MITRE
xt_sctp in netfilter for Linux kernel before 2.6.17.1 allows attackers to cause a denial of service (infinite loop) via an SCTP chunk with a 0 length.
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Analysis
by VulDB Data Team • 07/12/2021
The vulnerability described in CVE-2006-3085 affects the xt_sctp extension within the netfilter framework of Linux kernels prior to version 2.6.17.1. This flaw exists in the packet filtering subsystem that handles SCTP protocol traffic, specifically within the connection tracking module. The issue manifests when the kernel processes SCTP chunks that contain a zero-length field, creating a condition that leads to an infinite loop during packet processing. This represents a classic denial of service vulnerability that can be exploited by remote attackers without requiring authentication or special privileges.
The technical root cause of this vulnerability lies in the improper validation of SCTP chunk headers within the xt_sctp module. When processing an SCTP chunk with a zero length field, the kernel's packet handling code enters an infinite loop due to insufficient boundary checking and validation mechanisms. This flaw falls under the category of improper input validation as classified by CWE-20, where the system fails to properly validate or sanitize input data before processing. The vulnerability specifically impacts the kernel's SCTP connection tracking functionality, which is responsible for maintaining state information about SCTP connections passing through the firewall.
The operational impact of this vulnerability is significant as it allows remote attackers to cause a denial of service condition that can render the affected system unusable. An attacker can craft malicious SCTP packets with zero-length chunks and send them to a target system running an affected kernel version. The infinite loop consumes system resources continuously, potentially leading to system instability, service unavailability, and complete system hang. This type of attack aligns with the ATT&CK technique T1499.004 for network denial of service and represents a fundamental reliability issue in the kernel's packet processing pipeline.
Mitigation strategies for this vulnerability include applying the official kernel security patch released with version 2.6.17.1, which implements proper validation of SCTP chunk lengths and prevents the infinite loop condition. Organizations should also implement network segmentation and firewall rules that can filter or drop suspicious SCTP traffic, particularly chunks with invalid length fields. Additionally, monitoring systems should be configured to detect unusual packet processing patterns or resource consumption spikes that may indicate exploitation attempts. The fix addresses the core issue by implementing proper bounds checking and loop termination conditions in the SCTP chunk processing logic, ensuring that zero-length fields do not cause the kernel to enter indefinite processing loops. This vulnerability highlights the importance of robust input validation in kernel space code and demonstrates how seemingly minor protocol field validation issues can result in critical system stability problems.