CVE-2018-0051 in Junos
Summary
by MITRE
A Denial of Service vulnerability in the SIP application layer gateway (ALG) component of Junos OS based platforms allows an attacker to crash MS-PIC, MS-MIC, MS-MPC, MS-DPC or SRX flow daemon (flowd) process. This issue affects Junos OS devices with NAT or stateful firewall configuration in combination with the SIP ALG enabled. SIP ALG is enabled by default on SRX Series devices except for SRX-HE devices. SRX-HE devices have SIP ALG disabled by default. The status of ALGs in SRX device can be obtained by executing the command: show security alg status Affected releases are Juniper Networks Junos OS: 12.1X46 versions prior to 12.1X46-D77; 12.3X48 versions prior to 12.3X48-D70; 15.1X49 versions prior to 15.1X49-D140; 15.1 versions prior to 15.1R4-S9, 15.1R7-S1; 15.1F6; 16.1 versions prior to 16.1R4-S9, 16.1R6-S1, 16.1R7; 16.2 versions prior to 16.2R2-S7, 16.2R3; 17.1 versions prior to 17.1R2-S7, 17.1R3; 17.2 versions prior to 17.2R1-S6, 17.2R2-S4, 17.2R3; 17.3 versions prior to 17.3R1-S5, 17.3R2-S2, 17.3R3; 17.4 versions prior to 17.4R2. No other Juniper Networks products or platforms are affected by this issue.
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Analysis
by VulDB Data Team • 05/23/2023
The vulnerability described in CVE-2018-0051 represents a critical denial of service weakness within the Session Initiation Protocol application layer gateway component of Juniper Networks Junos OS platforms. This flaw specifically targets devices that operate with Network Address Translation or stateful firewall configurations while simultaneously having the SIP ALG functionality enabled. The issue manifests as a crash of critical system processes including MS-PIC, MS-MIC, MS-MPC, MS-DPC, or the SRX flow daemon (flowd) process. The vulnerability demonstrates particular significance in network security appliances where SIP ALG is actively utilized for managing VoIP traffic through firewall configurations.
The technical implementation of this vulnerability stems from improper handling of SIP protocol messages within the ALG framework of Junos OS. When the SIP ALG component processes malformed or specially crafted SIP packets, it fails to properly validate input parameters, leading to memory corruption or buffer overflow conditions that ultimately cause the targeted system processes to terminate unexpectedly. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities. The flaw operates at the application layer gateway level, where the system attempts to maintain state information for SIP sessions while performing protocol translation, creating multiple potential entry points for exploitation.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall network infrastructure reliability. When the flowd process or associated MS-* processes crash, the device loses its ability to maintain stateful firewall connections and NAT mappings, effectively breaking network connectivity for active sessions. This situation creates a cascading effect where legitimate users experience sudden disconnections while the device remains operational but unable to process new traffic. The vulnerability affects multiple device series including SRX Series appliances where SIP ALG is enabled by default, making it particularly dangerous in production environments where VoIP services are critical. According to ATT&CK framework category T1499, this vulnerability represents a denial of service attack that can be classified under the "Endpoint Denial of Service" technique, where an attacker targets specific system processes to cause service disruption.
Mitigation strategies for this vulnerability require immediate implementation of security patches provided by Juniper Networks for all affected versions of Junos OS. Organizations should prioritize upgrading to the latest stable releases that contain fixes for this specific issue, particularly focusing on versions mentioned in the advisory such as 12.1X46-D77, 12.3X48-D70, 15.1X49-D140, and subsequent releases. Alternative mitigation approaches include disabling the SIP ALG functionality on devices where it is not required, which can be accomplished through the command line interface using the appropriate configuration commands to disable the ALG feature. Network administrators should also consider implementing monitoring solutions that can detect process crashes or abnormal behavior patterns that might indicate exploitation attempts. Additionally, organizations should review their network architecture to minimize reliance on SIP ALG functionality where possible, as this reduces the attack surface for this specific vulnerability while maintaining network security posture. The recommended approach combines immediate patch management with configuration hardening to prevent exploitation attempts that could lead to sustained network disruption.