CVE-2013-6958 in ScreenOS
Summary
by MITRE
Juniper NetScreen Firewall running ScreenOS 5.4, 6.2, or 6.3, when the Ping of Death screen is disabled, allows remote attackers to cause a denial of service via a crafted packet.
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Analysis
by VulDB Data Team • 06/04/2021
The vulnerability identified as CVE-2013-6958 affects Juniper NetScreen Firewalls operating on ScreenOS versions 5.4, 6.2, and 6.3 when the Ping of Death screen protection is disabled. This represents a critical denial of service weakness that exploits a fundamental flaw in the firewall's packet processing mechanism. The vulnerability specifically targets the handling of fragmented IP packets, where the firewall fails to properly validate packet boundaries and reassembly logic when the Ping of Death protection is turned off. This weakness falls under the CWE-129 vulnerability category, which deals with improper validation of array indices and buffer overflows that can lead to system instability and service disruption.
The technical exploitation of this vulnerability occurs when remote attackers craft malicious IP packets that contain oversized or malformed fragments that exceed the firewall's expected packet size limits. When the Ping of Death screen is disabled, the firewall's packet reassembly process becomes vulnerable to malformed data that can cause memory corruption or resource exhaustion. The flaw manifests during the packet fragmentation reassembly phase where the firewall's internal packet handling routines fail to properly validate the length and boundaries of incoming fragments. This creates a condition where the system can be overwhelmed by crafted packets that force the firewall to consume excessive memory resources or trigger internal processing errors that result in system crashes or complete service outages.
The operational impact of this vulnerability is severe for organizations relying on Juniper NetScreen firewalls, as it can lead to complete network service disruption and potential business continuity issues. Attackers can leverage this weakness to perform sustained denial of service attacks against firewall appliances, effectively rendering the network security infrastructure non-functional. The vulnerability is particularly dangerous because it requires minimal privileges to exploit and can be executed from remote locations without authentication. Network administrators may experience complete loss of network connectivity and security enforcement capabilities, as the firewall becomes unable to process legitimate network traffic while simultaneously being overwhelmed by malicious packets. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under the ATT&CK technique T1498, which involves network denial of service attacks.
Organizations should immediately implement mitigations including enabling the Ping of Death screen protection, upgrading to ScreenOS versions that address this vulnerability, and implementing network segmentation to limit the impact of potential exploitation. The recommended approach involves applying the latest security patches from Juniper, which typically include improved packet validation routines and enhanced memory management for fragmented packets. Additionally, network monitoring should be enhanced to detect unusual packet patterns that may indicate exploitation attempts. The mitigation strategy should also include implementing rate limiting and packet filtering rules that can help prevent the injection of malformed packets that could trigger the vulnerability. Organizations should also consider deploying intrusion detection systems that can identify and block suspicious packet patterns associated with this specific attack vector, ensuring that the firewall's operational integrity remains intact against such targeted denial of service attacks.