CVE-2020-1671 in Junos
Summary
by MITRE • 10/17/2020
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash with a core dump if a malformed DHCPv6 packet is received, resulting with the restart of the daemon. This issue only affects DHCPv6, it does not affect DHCPv4. This issue affects: Juniper Networks Junos OS 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.2X75 versions prior to 18.2X75-D65; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.2 version 19.2R2 and later versions; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R1-S3, 20.1R2; This issue does not affect Juniper Networks Junos OS prior to 17.4R1.
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Analysis
by VulDB Data Team • 11/20/2020
The vulnerability identified as CVE-2020-1671 represents a critical denial of service weakness in Juniper Networks Junos OS platforms operating as DHCPv6 local servers or DHCPv6 Relay Agents. This flaw manifests within the Dynamic Host Configuration Protocol Daemon (JDHCPD) process, which is responsible for managing IPv6 dynamic host configuration services. The issue arises specifically when the daemon receives malformed DHCPv6 packets, causing it to crash with a core dump and subsequently restart. This behavior constitutes a significant operational risk as it directly impacts network availability and service continuity for devices relying on IPv6 addressing configuration. The vulnerability is particularly concerning because it affects multiple Junos OS version streams across different release branches, indicating a widespread exposure across the Juniper product portfolio.
The technical nature of this vulnerability can be categorized under CWE-122, which describes "Heap Overflow" conditions, though the specific manifestation here involves memory corruption during packet processing. The flaw occurs during the parsing and handling of DHCPv6 packets, where insufficient input validation allows malformed data to trigger buffer overflows or memory corruption within the JDHCPD process. This type of vulnerability falls under the ATT&CK technique T1499.004, specifically "Endpoint Denial of Service," where adversaries can cause system services to become unavailable through targeted packet injection. The root cause lies in inadequate bounds checking and input sanitization within the DHCPv6 packet processing routines, allowing attackers to craft malicious packets that exploit memory handling deficiencies in the daemon's implementation.
Operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network infrastructure reliability and availability. When the JDHCPD process crashes and restarts, IPv6 clients lose their ability to obtain dynamic addressing configuration, leading to complete network partitioning for IPv6 services. The cascading effect of such crashes can be particularly severe in enterprise environments where IPv6 services are critical for modern network operations, potentially affecting thousands of devices simultaneously. Network administrators face the challenge of maintaining service availability while implementing patches, as the crash condition occurs immediately upon receipt of malformed packets. The vulnerability affects a broad range of Junos OS versions, making it particularly dangerous as organizations across multiple release cycles require remediation, and the patching process can introduce operational complexity due to the critical nature of network services.
Mitigation strategies for CVE-2020-1671 should prioritize immediate implementation of official Juniper security patches for affected versions, as these contain the necessary code fixes to properly validate DHCPv6 packet structures. Network administrators should also implement ingress filtering and access control lists to restrict DHCPv6 traffic from untrusted sources, effectively limiting the attack surface. The implementation of network segmentation and monitoring solutions can provide early detection of malformed packet traffic patterns, enabling proactive response to potential exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments to identify all Junos OS devices running DHCPv6 services and ensure comprehensive patch deployment across all affected platforms. The remediation process should include testing in non-production environments to validate that patches do not introduce compatibility issues with existing network configurations while maintaining the critical requirement for network availability and service continuity throughout the remediation period.