CVE-2018-0057 in Junos
Summary
by MITRE
On MX Series and M120/M320 platforms configured in a Broadband Edge (BBE) environment, subscribers logging in with DHCP Option 50 to request a specific IP address will be assigned the requested IP address, even if there is a static MAC to IP address binding in the access profile. In the problem scenario, with a hardware-address and IP address configured under address-assignment pool, if a subscriber logging in with DHCP Option 50, the subscriber will not be assigned an available address from the matched pool, but will still get the requested IP address. A malicious DHCP subscriber may be able to utilize this vulnerability to create duplicate IP address assignments, leading to a denial of service for valid subscribers or unauthorized information disclosure via IP address assignment spoofing. Affected releases are Juniper Networks Junos OS: 15.1 versions prior to 15.1R7-S2, 15.1R8; 16.1 versions prior to 16.1R4-S12, 16.1R7-S2, 16.1R8; 16.2 versions prior to 16.2R2-S7, 16.2R3; 17.1 versions prior to 17.1R2-S9, 17.1R3; 17.2 versions prior to 17.2R1-S7, 17.2R2-S6, 17.2R3; 17.3 versions prior to 17.3R2-S4, 17.3R3; 17.4 versions prior to 17.4R2; 18.1 versions prior to 18.1R2-S3, 18.1R3.
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Analysis
by VulDB Data Team • 05/25/2023
This vulnerability exists within Juniper Networks MX Series and M120/M320 platforms operating in Broadband Edge environments where DHCP Option 50 is utilized for IP address requests. The flaw represents a critical deviation from expected network behavior where static MAC to IP address bindings should take precedence over dynamic DHCP requests. When a subscriber attempts to acquire a specific IP address through DHCP Option 50, the system incorrectly assigns the requested address regardless of existing static bindings in the access profile, creating a fundamental conflict in address assignment logic. This behavior violates standard network security principles where static bindings typically represent authorized and configured network resources that should take priority over dynamic requests.
The technical implementation of this vulnerability stems from improper validation within the DHCP address assignment process on Junos OS platforms. Specifically, the system fails to properly check for existing static MAC-to-IP bindings when processing DHCP Option 50 requests, allowing unauthorized IP address assignment that bypasses normal network access controls. This creates a scenario where a malicious actor could exploit the vulnerability by requesting specific IP addresses that are already statically bound to other devices, effectively enabling IP address spoofing and assignment conflicts. The vulnerability manifests as a failure to enforce proper address binding precedence rules, which is classified under CWE-284 Access Control Bypass in the Common Weakness Enumeration catalog.
The operational impact of this vulnerability extends beyond simple address assignment conflicts to create potential denial of service conditions and unauthorized information disclosure opportunities. Valid subscribers may experience service disruption when their legitimate IP assignments conflict with malicious requests, while unauthorized users could leverage this flaw to impersonate legitimate network devices. The vulnerability particularly affects Broadband Edge deployments where multiple subscribers share the same address pool, making it easier for attackers to identify and exploit overlapping IP assignments. This represents a significant security risk as it undermines the integrity of the network's address management system and could facilitate advanced persistent threats.
Mitigation strategies should focus on immediate patching of affected Junos OS versions to address the core validation flaw in DHCP Option 50 processing. Network administrators should implement additional monitoring and alerting mechanisms to detect unusual IP assignment patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1071.004 Application Layer Protocol: DNS where attackers might use IP spoofing to evade detection, and T1499.004 Unauthorized Access to Network Resources. Organizations should also consider implementing stricter DHCP server configurations that limit the scope of IP addresses available through Option 50 requests and establish robust network segmentation to minimize the impact of potential address conflicts. Regular network audits should verify that static MAC-to-IP bindings are properly enforced and that DHCP Option 50 behavior is consistent with network security policies.