CVE-2022-22211 in Junos OS Evolved
Summary
by MITRE • 10/18/2022
A limitless resource allocation vulnerability in FPC resources of Juniper Networks Junos OS Evolved on PTX Series allows an unprivileged attacker to cause Denial of Service (DoS). Continuously polling the SNMP jnxCosQstatTable causes the FPC to run out of GUID space, causing a Denial of Service to the FPC resources. When the FPC runs out of the GUID space, you will see the following syslog messages. The evo-aftmand-bt process is asserting. fpc1 evo-aftmand-bt[17556]: %USER-3: get_next_guid: Ran out of Guid Space start 1748051689472 end 1752346656767 fpc1 audit[17556]: %AUTH-5: ANOM_ABEND auid=4294967295 uid=0 gid=0 ses=4294967295 pid=17556 comm="EvoAftManBt-mai" exe="/usr/sbin/evo-aftmand-bt" sig=6 fpc1 kernel: %KERN-5: audit: type=1701 audit(1648567505.119:57): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=17556 comm="EvoAftManBt-mai" exe="/usr/sbin/evo-aftmand-bt" sig=6 fpc1 emfd-fpa[14438]: %USER-5: Alarm set: APP color=red, class=CHASSIS, reason=Application evo-aftmand-bt fail on node Fpc1 fpc1 emfd-fpa[14438]: %USER-3-EMF_FPA_ALARM_REP: RaiseAlarm: Alarm(Location: /Chassis[0]/Fpc[1] Module: sysman Object: evo-aftmand-bt:0 Error: 2) reported fpc1 sysepochman[12738]: %USER-5-SYSTEM_REBOOT_EVENT: Reboot [node] [ungraceful reboot] [evo-aftmand-bt exited] The FPC resources can be monitored using the following commands: user@router> start shell [vrf:none] user@router-re0:~$ cli -c "show platform application-info allocations app evo-aftmand-bt" | grep ^fpc | grep -v Route | grep -i -v Nexthop | awk '{total[$1] += $5} END { for (key in total) { print key " " total[key]/4294967296 }}' Once the FPCs become unreachable they must be manually restarted as they do not self-recover. This issue affects Juniper Networks Junos OS Evolved on PTX Series: All versions prior to 20.4R3-S4-EVO; 21.1-EVO version 21.1R1-EVO and later versions; 21.2-EVO version 21.2R1-EVO and later versions; 21.3-EVO versions prior to 21.3R3-EVO; 21.4-EVO versions prior to 21.4R2-EVO; 22.1-EVO versions prior to 22.1R2-EVO.
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Analysis
by VulDB Data Team • 10/18/2022
This vulnerability represents a critical resource exhaustion flaw in Juniper Networks Junos OS Evolved running on PTX Series devices, specifically targeting the Forwarding Plane Controller (FPC) components. The issue manifests through unlimited resource allocation within the FPC's GUID (Globally Unique Identifier) space, which serves as a fundamental component for tracking and managing forwarding table entries. The vulnerability stems from the evo-aftmand-bt process, which manages the forwarding table and maintains a finite pool of GUIDs for tracking packet forwarding states. When an unprivileged attacker continuously polls the SNMP jnxCosQstatTable, the system rapidly consumes available GUID space without proper cleanup or bounds checking mechanisms.
The technical implementation of this vulnerability exploits the lack of proper resource management within the FPC's application layer, where the evo-aftmand-bt process fails to enforce limits on GUID allocation requests. This process operates at the system level and manages the forwarding table entries for packet processing, making it a critical component for network functionality. The syslog messages indicate that when the GUID space is exhausted, the process triggers an assertion failure and subsequently terminates with a SIGABRT signal, which is a standard Unix termination signal indicating abnormal program termination. The audit logs confirm that the process was terminated due to resource exhaustion, with the specific error message showing "get_next_guid: Ran out of Guid Space" indicating the precise point of failure.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete system unavailability and manual intervention requirements. When the FPC resources become exhausted, the system generates alarms through the emfd-fpa process, which reports the application failure and triggers a red color-coded alarm indicating chassis-level issues. The subsequent system reboot occurs without graceful shutdown procedures, leading to ungraceful reboots that can result in packet loss and temporary network disruption. The affected FPC modules become completely unreachable through normal management interfaces, requiring manual restart procedures that can take several minutes to complete, potentially causing significant network downtime. This vulnerability aligns with CWE-400, which categorizes "Uncontrolled Resource Consumption" as a fundamental weakness in software design, and maps to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion attacks.
The mitigation strategy for this vulnerability requires immediate implementation of software updates to affected Junos OS Evolved versions, specifically targeting the releases mentioned in the advisory. Organizations should prioritize upgrading to versions 20.4R3-S4-EVO or later, 21.1R1-EVO or later, 21.2R1-EVO or later, 21.3R3-EVO or later, 21.4R2-EVO or later, and 22.1R2-EVO or later. Additionally, network administrators should implement SNMP access controls and monitoring to detect and prevent unauthorized polling of the jnxCosQstatTable, while also establishing automated alerting mechanisms to monitor FPC resource utilization. The monitoring commands provided in the advisory should be regularly executed to track GUID allocation patterns and identify potential abuse before it leads to system exhaustion. Network segmentation and access control measures should be implemented to restrict SNMP access to authorized management systems only, reducing the attack surface available to potential attackers. This vulnerability demonstrates the critical importance of resource management in network operating systems and highlights the need for proper bounds checking and allocation limits in system-level processes that manage forwarding table resources.