CVE-2007-4654 in SSHield
Summary
by MITRE
Unspecified vulnerability in SSHield 1.6.1 with OpenSSH 3.0.2p1 on Cisco WebNS 8.20.0.1 on Cisco Content Services Switch (CSS) series 11000 devices allows remote attackers to cause a denial of service (connection slot exhaustion and device crash) via a series of large packets designed to exploit the SSH CRC32 attack detection overflow (CVE-2001-0144), possibly a related issue to CVE-2002-1024.
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Analysis
by VulDB Data Team • 06/07/2025
The vulnerability identified as CVE-2007-4654 represents a critical denial of service weakness affecting SSHield 1.6.1 implementations within Cisco WebNS 8.20.0.1 software running on Cisco Content Services Switch series 11000 devices. This flaw specifically targets the SSH protocol implementation and manifests through the exploitation of SSH CRC32 attack detection mechanisms that were originally documented in CVE-2001-0144, with potential connections to CVE-2002-1024. The vulnerability operates at the network protocol level where specially crafted large packets can be transmitted to exhaust connection slots and ultimately cause complete device crashes, effectively rendering the targeted network infrastructure unavailable to legitimate users.
The technical implementation of this vulnerability stems from improper handling of cryptographic checksums during SSH protocol negotiation and data transmission phases. When the SSHield implementation processes large packets designed to exploit the CRC32 overflow mechanism, the system fails to properly validate or limit the resources consumed during checksum calculation and verification. This weakness creates a resource exhaustion condition where the device's connection management tables become saturated with invalid or malformed connection attempts, leading to a cascading failure that can ultimately result in complete system crash. The flaw operates within the context of the SSH protocol's integrity checking mechanisms, specifically targeting the CRC32 implementation that was designed to detect data corruption but has been repurposed by attackers to exploit resource management weaknesses.
From an operational perspective, this vulnerability presents a severe threat to network availability and business continuity for organizations relying on Cisco Content Services Switch infrastructure. The remote exploit capability means that attackers can initiate the denial of service condition from outside the network perimeter without requiring local access or authentication credentials. The impact extends beyond simple service interruption to include complete device unreliability, requiring manual intervention and potentially system reboots to restore normal operations. Network administrators face significant challenges in detecting and mitigating this attack vector as it operates at the protocol level and can be difficult to distinguish from legitimate network traffic patterns, particularly when attackers use sophisticated packet crafting techniques to avoid simple signature-based detection mechanisms.
The vulnerability aligns with several common weakness enumerations including CWE-129, which addresses improper validation of array indices, and CWE-399, which covers resource management issues. From an adversary perspective, this flaw maps directly to ATT&CK technique T1499.004, specifically targeting network denial of service conditions through resource exhaustion attacks. The attack pattern demonstrates characteristics of a protocol-based exploitation where the vulnerability is leveraged to consume system resources rather than to gain unauthorized access or execute malicious code. Organizations should implement immediate mitigations including network segmentation to isolate affected devices, firewall rules to limit SSH traffic from untrusted sources, and regular monitoring for unusual connection patterns. Additionally, the vulnerability highlights the importance of proper input validation and resource management in cryptographic protocol implementations, emphasizing that even well-established security mechanisms like CRC32 can become attack vectors when not properly constrained. The affected Cisco devices should be updated to patched firmware versions as soon as possible, with network administrators implementing comprehensive monitoring solutions to detect early signs of exploitation attempts.