CVE-2005-0356 in CacheOS
Summary
by MITRE
Multiple TCP implementations with Protection Against Wrapped Sequence Numbers (PAWS) with the timestamps option enabled allow remote attackers to cause a denial of service (connection loss) via a spoofed packet with a large timer value, which causes the host to discard later packets because they appear to be too old.
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Analysis
by VulDB Data Team • 07/05/2025
The vulnerability described in CVE-2005-0356 represents a critical flaw in TCP implementations that employ Protection Against Wrapped Sequence Numbers (PAWS) mechanisms with timestamp options enabled. This weakness specifically targets the way operating systems handle TCP sequence number validation when timestamp-based PAWS is active, creating a scenario where malicious actors can exploit the timing validation logic to disrupt network communications. The vulnerability operates at the transport layer of the TCP/IP protocol stack, fundamentally compromising the reliability of TCP connections in affected systems.
The technical flaw manifests when a remote attacker crafts and sends a spoofed TCP packet containing a large timestamp value that exceeds the expected range of the receiving system's timer. When the TCP implementation processes this packet, it applies the PAWS validation logic which compares the received timestamp against the system's current timer value. Due to the artificially inflated timestamp value, the system incorrectly determines that subsequent legitimate packets are too old and discards them accordingly. This behavior stems from the flawed timestamp validation algorithm that does not properly account for legitimate variations in timer values or edge cases in timestamp wrapping scenarios. The vulnerability is particularly insidious because it leverages the very security mechanism designed to protect against sequence number wrapping attacks, turning it into a vector for denial of service.
The operational impact of this vulnerability extends beyond simple connection disruption, as it can lead to cascading failures in network services that depend on reliable TCP communication. When systems begin discarding legitimate packets due to the spoofed timestamp values, network applications experience connection timeouts, service unavailability, and potential data loss. The attack can be executed from remote locations without requiring authentication or privileged access, making it particularly dangerous in production environments. Network administrators may observe intermittent connection failures, increased packet loss rates, and degraded service performance as affected systems struggle to maintain stable TCP connections. This vulnerability affects a broad range of TCP implementations across different operating systems and network equipment, making it a widespread concern for network security professionals.
Mitigation strategies for CVE-2005-0356 typically involve implementing kernel-level patches that correct the timestamp validation logic to properly handle edge cases and large timer values. System administrators should disable timestamp-based PAWS mechanisms when the vulnerability is present, though this reduces protection against sequence number wrapping attacks. Network segmentation and intrusion detection systems can help identify and block suspicious packet patterns associated with this attack. The vulnerability aligns with CWE-129, which addresses improper validation of input ranges, and maps to ATT&CK technique T1498, which covers network denial of service attacks. Organizations should also consider implementing rate limiting mechanisms and monitoring for unusual timestamp patterns to detect potential exploitation attempts. Regular security updates and proper configuration management are essential to prevent exploitation of this vulnerability across network infrastructure.