CVE-2020-1625 in Junos
Summary
by MITRE
The kernel memory usage represented as "temp" via 'show system virtual-memory' may constantly increase when Integrated Routing and Bridging (IRB) is configured with multiple underlay physical interfaces, and one interface flaps. This memory leak can affect running daemons (processes), leading to an extended Denial of Service (DoS) condition. Usage of "temp" virtual memory, shown here by a constantly increasing value of outstanding Requests, can be monitored by executing the 'show system virtual-memory' command as shown below: user@junos> show system virtual-memory |match "fpc|type|temp" fpc0: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2023 431K - 10551 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 fpc1: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2020 431K - 6460 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 user@junos> show system virtual-memory |match "fpc|type|temp" fpc0: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2023 431K - 16101 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 fpc1: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2020 431K - 6665 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 user@junos> show system virtual-memory |match "fpc|type|temp" fpc0: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2023 431K - 21867 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 fpc1: -------------------------------------------------------------------------- Type InUse MemUse HighUse Requests Size(s) temp 2020 431K - 6858 16,32,64,128,256,512,1024,2048,4096,65536,262144,1048576,2097152,4194304,8388608 This issue affects Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S6; 17.1 versions prior to 17.1R2-S11, 17.1R3-S1; 17.2 versions prior to 17.2R2-S8, 17.2R3-S3; 17.2X75 versions prior to 17.2X75-D44; 17.3 versions prior to 17.3R2-S5, 17.3R3-S6; 17.4 versions prior to 17.4R2-S5, 17.4R3; 18.1 versions prior to 18.1R3-S7; 18.2 versions prior to 18.2R2-S5, 18.2R3; 18.2X75 versions prior to 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60; 18.3 versions prior to 18.3R1-S5, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R2-S2, 18.4R3; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S3, 19.2R2. This issue does not affect Juniper Networks Junos OS 12.3 and 15.1.
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Analysis
by VulDB Data Team • 05/17/2024
The vulnerability described in CVE-2020-1625 represents a critical memory management flaw within Juniper Networks Junos OS operating systems, specifically affecting kernel-level memory allocation patterns when Integrated Routing and Bridging configurations are implemented with multiple underlay physical interfaces. This issue manifests as a persistent memory leak through the temporary memory allocation mechanism, where the "temp" virtual memory type shows continuously increasing Requests values when interface flapping occurs. The vulnerability operates at the kernel level and impacts the fundamental memory management subsystem, making it particularly dangerous as it can lead to system instability and extended denial of service conditions.
The technical root cause of this vulnerability lies in improper memory deallocation within the kernel's virtual memory management system when handling interface flap events in IRB configurations. When multiple physical interfaces are configured under a single IRB instance and one interface experiences flapping behavior, the system fails to properly release allocated temporary memory structures, resulting in a gradual accumulation of memory usage. This memory leak specifically affects the "temp" memory type which is used for temporary kernel allocations during routing and bridging operations, as evidenced by the continuous increase in Requests values shown in the virtual-memory output. The issue is particularly pronounced in systems where the memory allocation patterns are not properly cleaned up after interface state changes, creating a persistent resource exhaustion condition.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can significantly degrade system performance and availability. The continuously increasing memory usage affects running daemons and processes, potentially causing system instability, application crashes, and ultimately leading to extended denial of service conditions that can impact network connectivity and services. The vulnerability affects a wide range of Junos OS versions, spanning from 16.1 through 19.2 releases, with specific patch levels required for remediation. The memory leak occurs during normal operational conditions when interface flapping is detected, making it particularly insidious as it can persist for extended periods without immediate detection.
Security implications of this vulnerability align with CWE-401, which addresses improper release of memory, and can be mapped to ATT&CK technique T1499.004 for resource exhaustion attacks. The vulnerability enables an attacker to potentially cause sustained system degradation through memory exhaustion, particularly when interface flapping is induced or occurs naturally due to network instability. The affected systems represent a significant attack surface for denial of service attacks, as the memory leak can be exploited to gradually consume system resources until critical services become unavailable. Organizations should implement immediate patching strategies targeting the affected Junos OS versions, particularly focusing on the specific release branches mentioned in the advisory. Additionally, monitoring virtual memory usage patterns and implementing alerting mechanisms for unusual increases in temp memory Requests can provide early detection of this vulnerability's manifestation. Network administrators should also consider implementing interface stability monitoring and proactive interface flap detection to minimize the occurrence of conditions that trigger this memory leak behavior.