CVE-2020-1632 in Junos
Summary
by MITRE
In a certain condition, receipt of a specific BGP UPDATE message might cause Juniper Networks Junos OS and Junos OS Evolved devices to advertise an invalid BGP UPDATE message to other peers, causing the other peers to terminate the established BGP session, creating a Denial of Service (DoS) condition. For example, Router A sends a specific BGP UPDATE to Router B, causing Router B to send an invalid BGP UPDATE message to Router C, resulting in termination of the BGP session between Router B and Router C. This issue might occur when there is at least a single BGP session established on the device that does not support 4 Byte AS extension (RFC 4893). Repeated receipt of the same BGP UPDATE can result in an extended DoS condition. This issue affects Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S6; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R2-S11, 17.1R3-S2; 17.2 versions prior to 17.2R1-S9, 17.2R2-S8, 17.2R3-S3; 17.2X75 versions prior to 17.2X75-D105, 17.2X75-D110, 17.2X75-D44; 17.3 versions prior to 17.3R2-S5, 17.3R3-S7; 17.4 versions prior to 17.4R2-S8, 17.4R3; 18.1 versions prior to 18.1R3-S8; 18.2 versions prior to 18.2R2-S6, 18.2R3-S2; 18.2X75 versions prior to 18.2X75-D12, 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D51, 18.2X75-D60; 18.3 versions prior to 18.3R1-S6, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R1-S5, 18.4R3; 18.4 version 18.4R2 and later versions; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S2, 19.2R2. This issue does not affect Juniper Networks Junos OS prior to 16.1R1. This issue affects Juniper Networks Junos OS Evolved prior to 19.2R2-EVO.
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Analysis
by VulDB Data Team • 05/27/2024
This vulnerability represents a significant denial of service condition within the Border Gateway Protocol implementation of juniper networks junos operating systems and junos os evolved platforms. The flaw manifests when specific malformed bgp update messages are processed by affected devices, leading to cascading effects that terminate legitimate bgp sessions with neighboring peers. The vulnerability specifically targets devices that maintain bgp sessions without 4 byte as extension support as defined in rfc 4893, creating a condition where a single malicious update can propagate invalid messages through the network topology. The technical mechanism involves the device's bgp processing logic failing to properly validate incoming update messages before forwarding them to other peers, resulting in malformed updates that cause peer termination.
The operational impact of this vulnerability extends beyond simple service disruption to create potential network instability and routing chaos. When a device receives the specific malformed bgp update, it generates an invalid update message that gets propagated to other bgp peers, causing them to drop their established sessions. This creates a denial of service condition that can affect network connectivity and routing stability across the affected infrastructure. The vulnerability is particularly concerning because repeated receipt of identical malicious updates can maintain extended denial of service conditions, potentially requiring manual intervention to restore normal operation. The issue affects a broad range of junos os versions spanning from 16.1 through 19.2 releases, indicating this was a persistent flaw in the bgp implementation.
Network security professionals should recognize this vulnerability as a classic example of protocol processing flaws that can be exploited for denial of service attacks. The issue aligns with common attack patterns described in the mitre attack framework under the network denial of service technique, specifically targeting the bgp protocol which is fundamental to internet routing operations. From a compliance perspective, this vulnerability would be classified under cwe-248, representing an unchecked return value or exception in a protocol implementation, and potentially cwe-129, indicating improper input validation in network protocol handling. The vulnerability's exploitation requires minimal privileges and can be executed through network-based attacks, making it particularly dangerous in production environments where bgp stability is critical for internet connectivity.
Mitigation strategies should focus on immediate patching of affected junos os versions to the recommended security releases, which address the core bgp update validation logic. Network administrators should also implement bgp update filtering and monitoring to detect anomalous update patterns that might indicate exploitation attempts. Additionally, configuring devices to disable 4 byte as extension support where not required can prevent the vulnerability from being triggered through affected session types. The recommended approach involves applying vendor security advisories and ensuring all bgp peers are updated to versions that contain the patched bgp update message validation logic. Organizations should also consider implementing network segmentation and access controls to limit exposure to potentially malicious bgp update messages from untrusted peers.